Doctoral Degrees (Zoology and Entomology)
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Item Open Access Aspekte van die algemene biologie van Culex (culex) theileri Theobald (Diptera: Culicidae)(University of the Free State, 1984-01) Van der Linde, Theunis Christiaan De Klerk; Van Pletzen, R.; Hewitt, P. H.English: Since little is known of the occurence, distribution and possible vector roles of mosquitoes in the western Orange Free State, a trapping survey was undertaken to determine the species richness, relative abundance and seasonal fluctuations of mosquitoes in this region. Trapping of mosquitoes was done at weekly intervals from 1976 to 1978 on the farm Daniëlskuil, 30 km west of Bloemfontein. Twentyfive species were found to be present, of which eight had not previously been recorded from the Orange Free State. Culex (Culex) theileri Theobald was the most abundant species, accounting for 55,44% of the total catch. The temporal distribution and abundance of the seven dominant species viz. Aedes caballus, Ae. juppi, Ae. lineatopennis, Ae. durbanensis-group, Anopheles squamosus, Cx. theileri and Cx. univittatus were analyzed in terms of meteorological parameters such as air temperature, water temperature, relative pumidity and rainfall, all of which were recorded continuously. From these it was concluded that temperature and saturation deficit proved to be the most important variables. A Cx. theileri colony was established in the laboratory. Field observations and laboratory experiments led to the following rearing procedure and environmental conditions: Adults were held at 27°C and 65% RH with a day-night cycle of 12 hours each, which included a dawn and a dusk of one hour each respectively. Adults were fed on 7,5% sugar water and pigeons were used for bloodmeals. Optimum oviposition occured when individual gravid females were placed in pill vials containing 10 ml of water in which larvae had developed. Larvae were held in 0,02 M NaCI in shallow pans at 27°C. They were fed a mixture of brewer's yeast and an infant cereal. An electronmicroscopic study of the surface structure of the eggs revealed that the exochorion of the egg can be divided into four main regions viz. an anterior pole, a transitional region, an attachment region and a posterior pole. A cup-shaped corolla filled with gelatine-like material is present on the anterior pole and a prominent oil droplet on the posterior pole. In the attachment area the exochorion bears knobs with gaps between them. The knobs of adjacent eggs are arranged in such a way that adjacent eggs are joined to one another in a similar way as a press-stud operates. The eggs are thus held together to form a raft. Mating before or after a bloodmeal had no significant effect on the number of eggs produced. Intake of sugar after a bloodmeal had a detrimental effect on the number of egg-rafts produced, but not on the number of eggs per raft. Females which fed on white rats produced significantly more eggs than those which had fed on pigeons. The females, however, which fed on male rats produced large numbers of nonviable eggs. Aging prior to a bloodmeal resulted in decreased egg production. Repeated bloodmeals and oviposition by young females did not cause a decline in egg production or viability. Females oviposited during late dusk. They preferred 0,01 - 0,08 M NaCl solutions with a dark background. Furthermore, solutions in which larvae or pupae were reared, or which contained bacteria, were even more attractive. If offered no choice females oviposted on the available aqueous solution. Although temperatures below 15°C and above 33°C had a detrimental effect on oögenesis, no effect on selection of a suitable oviposition site could be established. The eggs are not particularly temperature sensitive during embryogenesis, but hatching does not occur below 12°C or above 36°C. The optimum developmental temperature was 27°C. NaCI concentrations above 0,08 M led to a decrease in the hatching percentage, while above 0,16 M no hatching took place. The temperature extremes of 12°C and 36°C were lethal to the larvae. The optimum temperature was 27°C. Increases in NaCI concentration up to 0,06 M had only a slight effect of larval developmental time. Thereafter a rapid increase in mortality occured. A direct correlation between survival of adults, temperature and saturation deficit was established. Sugar and bloodfed females survived longer at temperatures 6°C - 24°C and saturation deficits of 0,4 and 0,8 kPa. The results obtained form both field and laboratory studies were used in an attempt to explain the occurrence, temporal distribution and abundance of Cx. theileri.Item Open Access Studies on stalk borers of maize and sorghum in Lesotho(University of the Free State, 1998-11) Ebenebe, Adama Audu; Van den Berg, Johnnie; Van der Linde, T. C de K.English: Investigations on various aspects of stalk borers of maize and sorghum were conducted in Lesotho during the 1995/96, 1996/97 and 1997/98 growing seasons. Aspects investigated were their distribution and relative abundance on these two crops; seasonal moth flight pattern of Busseola fusca; impact of natural stalk borer populations on maize and sorghum; response of some maize and sorghum varieties/hybrids to artificial infestations with B.fusca and Chilo partellus respectively; farmers' perceptions and farm management practices with regard to the management of stalk borers; relative efficacy of insecticides used for C. partellus control in Lesotho; effect of planting date of maize on B.fusca infestations; effect of intereropping with beans on B. fusca infestations in maize, and relative abundance of natural enemies of B. fusca and C. partellus. These investigations provided the following results: B. fusca was distributed throughout Lesotho and was important on both maize and sorghum. C. partellus occurred only in the central lowlands where it attacked only sorghum. Seasonal B. fusca moth flight activity was characterised by distinct periods of high and low activity, with three and two to three generations of moths per season in the lowlands and mountains respectively. Infestations of B. fusca in Lesotho caused substantial yield losses in susceptible maize varieties and hybrids. Lesotho's maize varieties and hybrids were observed to be susceptible, with yield losses of up to 39.4% observed under field conditions. Their susceptibility was further demonstrated through artificial infestations in glasshouse and field studies. The glasshouse study showed that the levels of antibiosis and antixenosis resistance to B. fusca in these varieties and hybrids were low, while the field studies showed only moderate resistance to foliar damage. Lesotho's sorghum varieties exhibited susceptibility to stalk borer damage, both under field conditions and artificial infestations with C. partellus. A glasshouse study also found antibiosis to be the main resistance mechanism against C. partellus larvae in whorls of resistant sorghum genotypes. The variety Tenant White, exhibited tolerance to damage, both under natural and artificial infestations.Lesotho's farmers regarded stalk borers as important pests. The commonly employed control measure was insecticide application. Although the use of routine farm management practices has potential for suppressing borer populations, they were not utilised in this regard. Comparison of the efficacy of six insecticides used for stalk borer control in Lesotho indicated granular formulations beta-cyfluthrin 0.05 % and carbaryl 2.5 % to be more effective against C. partellus larvae in sorghum whorls than spray formulations. Early planting of maize (in November) substantially reduced damage and yield loss caused by B.fusca. Intereropping maize with beans reduced damage and yield loss caused by B. fusca in maize. Furthermore, alternating rows of maize with rows of beans was more effective than alternating maize with beans within a row. The braconids Bracon sesamiae, Cotesia sesamiae, Euvipio sp. and Habrobracon brevicornis parasitized B. fusca larvae. Only B. sesamiae and C. sesamiae were recorded on C. partellus larvae. An unidentified ichneumonid was reared from C. partellus pupae, while a red ant species Dory/us sp. (Formicidae) was recorded as a predator of both B. fusca and C. partellus larvae. However, the activity of these natural enemies was generally low, increasing only towards the end of the growing season. These investigations have shown that stalk borer infestations are economically important in Lesotho. However, adopting such cultural practices as planting date adjustment, intereropping and destruction of crop residues can limit infestations. These practices, together with limited insecticide use, should form components of an integrated stalk borer management system. Future research efforts in Lesotho need to include the identification and development of maize and sorghum varieties and hybrids with high yields even under stalk borer infestations. Where such varieties are open-pollinated, they will be of particular benefit to the resource-poor farmers, who may not be able to afford hybrid seeds.Item Open Access The bio-ecology and control of Coproica vagans and Coproica hirtula (diptera: Sphaeroceridae) in cattle feedlots(University of the Free State, 1998-12) Badenhorst, Daniel; Van der Linde, T. C. D. K.; Louw, S. V. D. M.English: Sphaeroceridae are generally known as "lesser dung flies". These are small to medium sized dark-brown to blackish flies ranging from about 0.5 mm to 6 mm in length. They are saprophagous and occur throughout the tropical and subtropical regions of the world. A unique scenario involving Sphaeroceridae flies that constitute a serious problem at South African feedlots is discussed. Two species, namely Coproica vagans (Haliday) and Coproica hirtula (Rondani) are both associated with cattle dung at feedlots, with the former species reflecting dominance. The flies cause a nuisance to the cattle by forming black clouds of swarming flies. It therefore became imperative to find a way to control these flies. The establishment of separate sphaerocerid laboratory colonies from which experimental studies could be conducted was successful and is described. The seasonal occurrence and relative abundance of the Diptera fauna occurring within undisturbed cattle droppings exposed to shaded and sunny locations in the central Free State was investigated. The Sphaeroceridae was of particular interest, but only five presumably new species were discovered among the 21 fly species reared from these droppings. No C. vagans or C. hirtula specimens were encountered. The influence of physical parameters such as temperature and moisture content of the dung on the development and survival of immature stages and adult flies is described. Temperature had a major effect on all stages of both species, and both too low and too high temperatures led to severe mortality. Optimum developmental temperatures were between 24°C and 30°C. The development time of all stages also increased with a decrease in temperature. Moisture content of the dung had the same influence on all stages of the Sphaeroceridae, and optimum moisture content levels were at approximately 90%. Development times also increased somewhat with a decrease in moisture content levels of the dung. Oviposition by adult females of both sphaerocerid species and the influence of temperature and photo periodicy was determined and is described. Oviposition continued for more than 60 days at colder temperatures, although the number of eggs produced was often very low. Higher temperatures on the other hand resulted in large numbers of eggs produced by sphaerocerid females (up to 607 eggs per female) at 24°C, but the duration of oviposition dropped. Different photoperiods had no severe effect on oviposition or egg production. Development and survival of immature stages and adult Sphaeroceridae were also influenced by the type of dung which they were offered and the effect of this phenomenon on the flies is also described. Some dung types, e.g. horse, buffalo and rhino dung, had a negative influence on larval and adult survival most probably as a result of the higher fiber contents of these dung types. The other dung types such as cattle, sheep and elephant dung, led to successful development and survival of all stages. Biological control was attempted with several Coleoptera (a staphylinid, Philonthus caffer (Boheman) and scarabaeids Aphodius pseudolividus Balthasar and Harmogaster strydomi Endrëdi), Diptera (Musea xanthomelas Wiedemann and Coboldia fuscipes (Meigen)) and mite species. These biological control agents all failed to control Sphaeroceridae numbers mainly because of their inability to survive in wet feedlot dung. Chemical control on the other hand produced positive results and seemed like the only option available. Several insecticides and chemicals were tested but only two, namely Neporex (cyromazine) and Scatterkill (piperonyl butoxide), showed irradication potential. A further advantage of Scatterkill is its long residual effect in feedlot dung.Item Open Access Branchial monogenean parasites (Monogenea: Dactylogyridae) of characin fishes from the Okavango river and Delta, Botswana(University of the Free State, 1998-12) Christison, Kevin William; Van As, J. G.; Basson, LindaEnglish: The fishes of the Okavango System, Botswana, are of considerable economical and ecological importance. Recently, scientists and local fishermen have reported a dramatic decline in the fish stocks of the Okavango River and Delta. There are many reasons for this decline to which fish parasites ~may at least be a contributing factor. In recent surveys to the Okavango, monogeneans have been found to be of the most prominent parasites infesting the Okavango fishes. The tigerfish, Hydrocynus vittatus Castelnau 1861, especially, show high infestations of the branchial monogeneans, Annulotrema pikei (Price, Peebles & Bamford 1969). The genera Annulotrema Paperna & Thurston 1969 and Characidotrema Paperna & Thurston 1968, are exclusively parasites of characiform fish in Africa. In the Okavango the characiforms are represented by five species, Brycinus lateralis ( Boulenger 1900), Hepsetus odoe (Bloch 1794), Hydrocynus vittatus, Mieralestes acutidens (Peters 1852) en Rhabdalestes maunensis (Fowler 1935), all of which, are infested by species of the genus Annulotrema and only one, Brycinus lateralis (Boulenger 1900), is infested by a species of the genus Charcidotrema. During two field trips to the Okavango System, five Annulotrema species were collected; three of which are known species and two new species. This is the first record of monogeneans from Botswana and represents the southern most distribution recorded of A. curvipenis Paperna 1969 & A. hepseti Paperna & Thurston 1969. Comparative descriptions of the three known species are given and the two new species are described as A. micralesti sp. n. and A. rhabdalesti sp. n. Mixed infestations of A. curvipenis and Characidotrema nursei Ergens 1973 were also recorded from the gills of Brycinus lateralis. This also represents the southernmost, recorded distribution of C. nursei. Investigation of histological sections revealed that although these monogeneans occurred in relatively high numbers on the gills of the fish, the pathology they caused was limited. Examination of the infestation statistics showed that these parasites exhibit site preferences to the gills on which they occurred. This preference is influenced by the number of monogeneans of the same or other species as well as the number of other parasites occurring on the gills of the fish hosts. When considering the results, these monogenean parasites do not seem to cause severe harm to the host fish. Any changes in the environment could alter the face of this parasite-host relationship dramatically and hence the potential pathogenicity of these parasites should, however, not be ignored.Item Open Access The ecology and ecophysiology of Marion Island house mice, Mus Musculus L.(University of the Free State, 1999) Avanant, Nico Loubser; Kok, O. B.; Smith, V. R.English: This thesis presents the results of a studv of the biotic and abiotic conditions experienced by house mice on Marion Island, their morphological and reproductional adaptations to island conditions, the seasonal changes in their diet. and of the densities and biomasses of their prey items. By establishing burrow systems and sheltered aboveground runways nuce experience a microelimate that is far less harsh than the macroelimatie regime. In terms of warmth, this extends the season of mouse activity significantly compared with what would be allowed by the macroclimate. House mice are opportunistic feeders and this plays a major role in their survival under the harsh conditions on Marion Island. The mice are primarily carnivores and impact severely on soil macroinvertebrate populations, annually removing up to several times the average instantaneous standing crop of some macroinvertebrate populations. Since macroinvertebrates are cardinal agents of ecosystem functioning by being the main mediators of nutrient cycling on the island, their predation by mice has severe ecological implications. Between 1979/80 and 1992/93 the densities and biomasses of the mouse's major invertebrate prey species have decreased. The percentage composition of the various prey types in the macroinvertebrate population has also changed. These changes have caused changes in the composition of the mouse's diet. Seasonal changes in reproductive status, sex ratio, age structure, body mass and length, kidney- and adrenal mass, and length and shape of intestines were determined, in order to provide information concerning the house mouse's response to fluctuating environmental parameters and to assess the levels of stress experienced by mice at different times of the year. Stress levels are influenced by population density, sex, reproductive status, temperature and availability of food. In 1992/93 mice had significantly larger body to tail length ratios than in 1979/80, despite the fact that the island warmed considerably in the interim. This warming has allowed a significantly longer breeding season, perhaps by as much as two months. It is suggested that this is the reason that end of season densities are now considerably higher than in 1979/80.Item Open Access Aspekte van die ekologie van avifauna op 'n binnelandse lughawe(University of the Free State, 1999-11) Kok, Alettta Catharina; Kok, O. B.; Van der Linde, T. C. de K.English: Owing to the world-wide increase in air traffic the number and intensity of collisions between birds and aircraft have increased accordingly. Bird strikes are not only responsible for considerable physical damage and fmancial losses, but also endanger human lives unnecessarily. Aspects of the ecology of avifauna at the Bloemfontein airport were, therefore, investigated in order to reduce hazards posed by birds at inland airports. Plant surveys conducted during 1994 and 1995 confirm the classification of the study area as a chy Cymbopogon-Themeda veld type. Based on botanical composition and basal cover the veld is in a relatively good condition. Regularly mowed experimental plots were characterised by a greater variety of plant species consisting of a lower percentage of climax grasses and a larger component of pioneer grasses, forbs and dwarf shrubs compared to undisturbed tall grass areas. A total of 270 pitfall traps were used over a continuous period of 15 months to determine the diversity, relative abundance and seasonal variation of terrestrial invertebrates in the study area. Members of seven classes, 23 orders and 57 families were identified of which insects comprised the most important component by far. As .opposed to this, flying and plantliving invertebrates which were monitored on a monthly basis by means of sweep-nets were represented by only two classes, comprising 13 orders and 70 families. Mouse trapping and incidental catches of smaller vertebrates in pitfall traps suggest a limited presence of amphibia, reptiles and small mammals. Broadly speaking significantly more invertebrates were collected during the wet than during the dry season. Evidently, the opposite trend applies with regard to the sampling of reptiles and small mammals. Although no direct relationship between catches and rainfall as environmental factor could be demonstrated, a significant correlation with temperature was indicated. Over a period of eleven years approximately 5 000 individuals representing 51 bird species which, potentially, posed a threat to aviation were collected at the Bloemfontein airport. More than half of the species concerned can be considered as I medium-sized terrestrial birds of which the crowned plover (Vane/Ius coronatus) is by far the most important. A similar species composition occurred at the Kimberley airport, in contrast to the greater percentage of water associated birds at the Johannesburg airport. Indirectly, food availability appears to be one of the main environmental factors involved in the presence of, amongst others, the five dominant bird species at the Bloemfontein airport. Analyses of the stomach contents of 3 544 bird carcasses from the Bloemfontein airport, supplemented by 906 stomach contents from the Johannesburg and Kimberley airports, indicate that insects can generally be considered the main food source of the birds concerned. Based on dry mass composition the Isoptera, followed by the Coleoptera and Orthoptera, constitute the most important component in the diet. The Isoptera, more specifically the harvester telmite (Hodotermes mossambicusi), is, moreover, the only important prey taxon showing a conspicuous utilisation peak during the relative food shortage of the dry season. Evidently, temporary superabundant food sources which periodically come about in grassland habitats are opportunistically utilised by the birds. Indications are that habitat manipulation at airports can serve as an effective long-term bird control strategy. Based on the superabundant availability of invertebrate prey species in short grass areas compared to that in tall grass, a socalled tall grass policy would not only lead to the reduction of available food sources, but would also hamper the prey searching abilities of the largely insectivorous avifauna. According to results obtained, chemical manipulation can also be successfully employed to limit the presence of harvester termites, the staple food of the majority of terrestrial bird species in grassland habitat, thereby bringing about a reduction in bird numbers. At the same time, a five layered model is discussed setting out the responsibilities of all the role players associated with the implementation of a successful bird control programme. Key words: Airport, avifauna, bird hazard, feeding ecology, harvester termites, pitfall trapping, grassland, habitat manipulation, management.Item Open Access The biology of gnathiid isopod parasites and their role as vectors of fish blood parasites in South Africa(University of the Free State, 2000-12) Smit, Nicholas Jacobus; Van As, J. G.; Basson, Linda; Russell, Angela DaviesEnglish: Research on marine fish parasites has been largely neglected in South Africa. This is especially true for the temporary fish parasites of the isopod family Gnathiidae and fish blood parasites of the family Haemogregarinidae. In this study, surveys were carried out to determine the presence of gnathiid isopods and fish haemogregarines associated with different intertidal and sub-tidal fish hosts over a period of four years, at two different localities on the South African south coast. The study also focussed on the relationship between gnathiids and haemogregarines, specifically the possibility that the gnathiid Gnathia africana Barnard, 1914 might be a vector of the fish blood parasite Haemogregarina bigemina Laveran and Mesnil, 1901. Laboratory work was conducted to elucidate the life cycle of G. cfricana. It was found that G. cfricana has three larval stages, consisting of three unfed (zuphea) and three fed (praniza) stages, with the final stage praniza larvae moulting into either male or female adults. Forty days after their last feed as praniza 3 larvae, mature females release stage 1 zuphea larvae. Detailed information was also supplied on the feeding and digestion length for each larval stage. The females of G. africana were re-described from the material collected. Furthermore, other gnathiid larvae, not resembling any of the known species from South Africa, were collected from three species of elasmobranchs as well as the evileye pufferfish. Both groups of larvae were kept in the laboratory, where they moulted into adult males that did not conform to the description of any other gnathiid species in South Africa, or worldwide. These specimens were described as new species (Gnathia pantherinum sp. n. and G. pipindae sp. n.), using light and scanning electron microscope observations. Extensive information was also provided on the final life cycle stages of G panthertnum sp. n. Special attention was given to finding distinguishing characteristics to identify females and larvae of various species in the absence of males. Comparing material in this study with information from the literature showed that the morphology of the pleotelson and cephalosome appendages of females and larvae could be successfully used as differentiating characteristics. The research conducted on fish haemogregarines led to new distribution and host records for two known species, and the description of two new, but un-named species. Development stages of H. bigemina were found in the gut of G. africana larvae that had fed on H. bigemina-infected host fish. The data obtained from these results was used to compile a complete life cycle for H. bigemina in both the fish and the arthropod host.Item Open Access An integrated approach to pest management in field pea, Pisum sativum (L.), with emphasis on pea aphid, Acyrthosiphon pisum (Harris)(University of the Free State, 2002-03) Ahmed, Kemal Ali; Louw, S. V. D. M.; Swart, W. J.This study comprises investigations into pea aphid, Acyrthosiphon pisurn, and ascochyta blight damage on field pea, the evaluation of plant resistance levels in both breeding lines and cultivars, the identification of plant resistance and the underlying mechanisms, and cultural, chemical and biological control methods. Varietal resistance studies indicated that there were differences between the Ethiopian and the South African strains of pea aphid with regard to their survival and reproduction on the field pea genotypes evaluated. The field pea entries performed very well against the former strain compared with the latter. Three lines (Holetta Local-90, 305PS210687 and 061K-2P-2/9/2) performed well across both strains. Field pea lines exhibiting tolerance, antixenosis and antibiosis resistance to A. pisum were identified under greenhouse conditions. Some lines showing high levels of antibiosis to nymphal feeding were also found in both strains. This kind of resistance mechanism may promote insect biotype development through increased selection pressure on the pest population. Strain variation was also evident in tolerance, antixenosis and antibiosis resistance. The South African strain was the least aggressive across all entries. Of the 30 varietiesllines (including a local susceptible cultivar from Ethiopia) evaluated for resistance to isolates of Mycosphearella pinodes, Oregon Sugar Pod II had a 1.9 blight severity and was scored as resistant, three genotypes (Green Feast, Sugar Queen and line 304WAll01973) were scored as intermediate (2.1 - 3.0 severity factor) and the remaining 26 genotypes were scored as susceptible (3.1 - 4.0 severity factor) or highly susceptible (4.1 - 5.0 severity factor). In all scoring dates, significant differences occurred among genotypes, isolates and genotype x isolate interactions. However, the genotype x isolate interaction contribution to total variation was much lower than that of genotypes and isolates separately. The isolate of the Denbi site in Ethiopia was slightly more virulent than those of the Holetta and Kulumsa sites. Assessments regarding the potential of biological control of pea aphids using a predatory beetle (Hippodamia variegata) and entomopathogenic fungus (Beauveria bassiana) indicated that predator-treated plots supported significantly lower aphid numbers from the third week onwards, when compared to the fungus-treated and infested control plots. The degree of mycosis caused by Beauveria on pea aphids was 14.3% in week three after inoculation and the figure dropped to 2.5% in week 5. Percentage yield loss due to pea aphid in predator-treated plots was 8.3 % compared with 16.0 % in fungus-treated plots. Field pea intercropped with Ethiopian mustard sustained less pea aphid and ascochyta blight incidence, compared to faba bean, wheat and field pea mono crop at all locations studied. The land equivalent ratio for this particular mixed crop system exceeded 1.0, indicating that the mixed crops selected were efficient for yield and monetary outcome. The increase in efficiency was ascribed to the barrier effect of mustard plants in the intercrop set-up, which was significant in reducing pea aphid population size and disease severity. The effect of fertilizer application and sowing date on pea aphid and ascochyta blight severity was location specific. At the Holetta site in Ethiopia disease severity and pea aphid infestation were significantly reduced in fertilized plots compared with unfertilized plots, while it was only the disease that showed significant difference at the Denbi and Kulumsa sites. This indicates the importance of fertilizer application as a cultural control strategy for this disease. Neither early nor late sowing resulted in reduced aphid infestation and disease infection at any of the locations. Significant interactions between variety, sowing date and fertilizer for ascochyta blight was observed, indicating that the effect of one factor was influenced by the other two factors. For aphid population density and yield, the three factors had little or no effect on each other at the Denbi and Kulumsa sites. Cultivar Markos was moderately resistant to ascochyta blight and it gave higher yield compared to Mohanderfer and the varieties used by farmers. Neem seed kernel extract application was superior to Multineem", a commercial product, against pea aphid development and reproduction. The neem preparations significantly reduced the number of molts, longevity and fecundity of A. pisum in a concentration-dependent manner. The effect on young adults exposed to neem was not as drastic as in the case of immatures. Acute and chronic toxicity effects on pea aphid were noted showing that azadirachtin is an effective inhibitor of population growth of pea aphid both on treated plants and when topically applied to the insect. Host plant resistance and natural chemical (neem) pest control in large scale farming systems, or integrated with cultural and biological control in low-input subsistence farming systems provides effective management strategies for pea aphid and ascochyta blight in field pea. From this study, possible implementation of IPM in field pea is presented and includes aspects of varietal resistance and biological, cultural and chemical control.Item Open Access Branchial monogenean parasites (Monogenea: Dactylogyridae) of fishes from the Okavango River and Delta, Botswana(University of the Free State, 2002-06) Christison, Kevin William; Van As, J. G.; Basson, LindaEnglish: The Okavango Delta has received much popularity for the host of wildlife that it sustains. More recently it has gained increasing interest for the rich diversity of fish species that occur there. The fishes of the Okavango are also becoming increasingly important as a natural resource attracting revenue to Botswana in the forms of ecotourism and aquaculture and also as an important food source for the local community. The Okavango Delta is a flood driven system and much of the fish distribution throughout the Delta and the timing of certain behavioural activities are dependent on the timing and magnitude of the flood. For the purpose of determining the distribution of fish parasites throughout the system, the distribution of the fish hosts was determined and it was found that fish community structure could be used to distinguish different habitat types within the different ecological regions. Fifty-nine of the expected 68 fish species for the Delta have been collected. These species represent 12 families of which the families Cichlidae and the Cyprinidae are the most abundant, making up about 50 percent of the species collectively. Various parasites have been collected from these fishes of which the monogeneans seem to be the most prevalent and abundant and currently represent approximately 36% of the parasites collected. Most of the monogeneans recorded thus far were representatives of the subclass Polyonchoinea. Of these, all belonged to the families Dactylogyridae and Gyrodactylidae. Of the monogenean parasites infesting the Okavango fishes, the representatives of the family Dactylogyridae were the most diverse. Genera of African dactylogyrids are either endemic to Africa or belong to genera with wider geographical ranges. In general dactylogyrids are host specific and their zoo geographical affinities are therefore linked to the faunistic origin of their hosts. The distribution of dactylogyrid species within Africa is determined by the distribution pattern of their hosts. Twenty-two dactylogyrid species comprising seven genera were recorded, of these 10 species were previously undescribed. This study represents the first records of representatives of the class Monogenea from Botswana and hence the Okavango Delta.Item Open Access Reproductive processes of scyphidiid peritrichs associated with limpet and haliotid hosts along the coast of South Africa(University of the Free State, 2002-11) Peters, Helene; Basson, Linda; Van As, Liesl L.English: During the early 19th century a lot of progress was made in clarifying reproduction patterns and cycles in the kingdom Protozoa Goldfuss, 1818. During the first half of the 20th century various scientists studied the reproductive processes of peritrichs and made valuable contributions. While thousands of recent papers exist on reproduction of ciliates, not much work has been done on epibiontic peritrichs. In this study the processes of binary fission, telotroch formation and conjugation are described for Mantoscyphidia branchi Van As, Basson & Van As, 1998, M. marioni Van As, Basson & Van As, 1998, M. midae Botes, Basson & Van As, 2001 and M. spadiceae Botes, Basson & Van As, 2001. It was also determined whether binary fission, telotroch formation and conjugation occur in a new species of Ellbiophrya Peters, Van As, Basson & Van As, in prep. Haliotids were collected from 1997 to 2002 at the De Hoop Nature Reserve on the south coast of South Africa and were also obtained from the Danger Point Abalone Farm near Gansbaai, and the Abagold Farm in Hermanus. Limpets were collected from 1993 to 2002 from the Goukamma Nature Reserve, De Hoop Nature Reserve and Keurboom Beach on the south coast; Mc Dougall's Bay and the Olifants River Mouth on the west coast; Bazley and at the rocky shores of Lake St. Lucia on the east coast of South Africa; and on the east coast of Marion Island at Boulder Beach which is situated in the southern Indian Ocean. Live symbiont specimens undergoing reproduction were observed with light microscopy and photomicrographs were taken of the various stages of binary fission, conjugation and telotroch formation. Mayer's, Harris' and Heidenhain's Iron Hematoxylin were used to stain the nuclear apparatus. The details of the infundibulum were studied by staining Bouin's fixed smears with protargol. Gills were also examined using scanning electron microscopy. Binary fission was mostly observed in M. spadiceae and also occurred earlier in M. spadiceae than in M. branchi and M. midae populations. The formation of telotrochs was mostly observed in populations of M. branchi and M. spadiceae. Throughout this study it was uncertain whether binary fission always has to occur before a telotroch can develop, or whether binary fission follows telotroch formation. Conjugation was mostly observed in populations of M. branchi and M. midae. In the Ellobiophrya species conjugation was also observed and this is the first record of conjugation in the genus Ellobiophrya (Chatton & Lwoff, 1923). It would be possible to study all these processes in detail if a suitable medium could be cultured in future.Item Open Access Alternative methods of controlling the brown locust, Locustana pardalina (Walker)(University of the Free State, 2003-07) Price, Roger Edward; Van der Westhuizen, M. C.Outbreaks of the brown locust, Locustana pardalina (Walker), occur almost annually in the semi-arid Karoo region of South Africa and southern Namibia. Current suppressive control strategy relies on the application of fast-acting, synthetic pyrethroid insecticides, applied as ultra low volume drift sprays, to control gregarious brown locust targets at source within the Karoo outbreak region. However, the negative impact that the repeated application of insecticides may have on the rich diversity of endemic invertebrates and reptiles found in the Nama-Karoo biome is of great concern to landholders and conservationists. How to reduce the insecticide load and minimise the environmental impact in the Karoo and yet at the same time control this serious agricultural pest has become a controversial issue. There is thus an urgent need for more environmentally benign methods of locust control, as an alternative to the current spraying of insecticide. As part of a locust research project initiated by the Plant Protection Research Institute, Pretoria, the potential of various alternative methods of controlling the brown locust were evaluated against gregarious hopper populations in the laboratory and in the field. It was first important to update the available information on the background level of control provided by natural enemies and diseases of the brown locust. Although a range of natural enemies were found to prey upon the various life stages, their impact on brown locust populations in the present study was negligible. Of particular interest was a study of the impact of the sarcophagid fly, Wohlfarhtia pachytyli, which is a well-known facultative parasite of late instar brown locust hoppers and fledglings. However, field data suggested that the potential of the fly as a biological control agent may have been over estimated in the past, as the fly failed to cause more than 6% mortality of fledgling swarms in the present study. Before the first insecticides became available at the turn of the zo" century, farmers had to resort to mechanical methods to protect their crops and pastures from the ravages of locusts. Turning back the clock, the destruction of locust egg beds and the harvesting of locusts were re-examined as control methods. Excavation of locust eggs gave effective control, but the disturbance of the friable soils in the Karoo would damage the vegetation cover and cause severe erosion problems and is therefore not advocated. Harvesting of live locusts using nets or vacuum machines was not practical due to the avoidance behaviour of locusts. However, the harvesting of locust cadavers lying on the soil surface following insecticide spraying, once they had dried out and insecticide residues had broken down, was possible. With their high protein and fat content, the processing of locust cadavers into animal feed may become economically viable in future. Before organo-chlorine insecticides became available in the 1940s, bran bait containing sodium arsenite was extensively used for brown locust control. The baiting technique was re-evaluated in the present study using minute dose rates of the phenyl-pyrazol insecticide, fipronil, dissolved in water and mixed into wheat bran as the edible carrier. Bran bait containing 0.02% fipronil 200Se (Regent®) was prepared on site and was broadcast by hand onto the soil surface around bushes occupied by hopper bands as overnight roosting sites. Excellent control (>95%) of small and medium sized hopper bands was achieved, as long as baiting was undertaken shortly after sunrise, before hoppers scattered from the baited area. Baiting large band targets, or baiting later in the day once hoppers became active, was not effective. Baiting with 0.02% Regent® proved very effective if applied to compact, roosting hopper bands. It was also inexpensive and was easy to prepare and apply, requiring basic equipment and limited training. However, the logistics of the bulk transport, preparation and application of locust baits under operational conditions appear daunting. Insecticide barrier treatments using fipronil (Adonis® 5UL), applied to 21m-wide strips of Karoo vegetation at a dose rate of 12.5g a.i./ha, were used to intercept gregarious brown locust hopper bands marching through the veld. Barriers of Adonis® proved very effective against mobile L2-L3 bands and against small L4-L5 bands, giving >90% control within 48 hours. However, barriers sometimes failed to adequately control large and mobile L5 bands that had sufficient momentum to march through barriers before the majority of hoppers acquired a lethal dose of Adonis®. Barriers also proved less effective where the vegetation density was sparse or where the vegetation was unacceptable to locusts. The size and density of the hopper bands and the time of day when bands made contact with the barriers also appeared to influence efficacy. Despite these factors, Adonis® barriers were still considered to have potential for the control of brown locust hopper bands in the more remote areas of the Karoo, especially during the early stages of an outbreak when hopper bands are still young. However, barriers would have to be judiciously applied to restrict the environmental impact of Adonis® against non-target organisms. Large-scale operational trials are recommended. Insect Growth Regulators (IGRs) have shown promise when applied as barrier treatments against various locust and grasshopper species. However, laboratory experiments with the IGRs, flufenoxuron and teflubenzuron, applied to leaf discs and fed to L5 brown locust hoppers at dose rates of 3-l5Ilglg, gave variable mortality of 30-70%, with most mortality occurring as the hoppers attempted to moult. In another experiment, diflubenzuron (Dimilin OF6®), was sprayed onto maize plants at volume rates of l-3.f;ha and subsequently fed to L2 brown locust hoppers in the laboratory. Dimilin OF6® produced 100% mortality of L2 hoppers within Il days at all application rates, as long as hoppers were continuously exposed to treated vegetation. However, irregular exposure to Dimilin® during the inter-moult period produced unsatisfactory mortality, as the product is evidently non-accumulative and is readily excreted. The fact that brown locust hoppers have to be regularly exposed to IGR-treated vegetation, combined with the sporadic feeding behaviour and high mobility of brown locust hopper bands in the Karoo, would probably make IGR barriers unsuitable for brown locust control operations. In collaboration with nBC and the LUBILOSA programme (CABI Bioscience, Ascot, UK), the locust-killing fungus, Metarhizium anisopliae var. acridum, was imported and evaluated by PPRI locust researchers as a myco-insecticide agent in laboratory and field trials against the brown locust. Under suitable application conditions the myco-insecticide, applied at a standard dose rate of lOOgconidia/ha, regularly produced >90% mortality of hoppers maintained in cages, although speed of kill was slow, with median lethal times of 10.3 and 13.4 days for the ground and aerial application trials respectively. In most cases, acceptable >90% mortality was not achieved for at least three weeks after application. Despite the slow speed of kill, the myco-insecticide agent was considered a significant advance in locust control and the product was subsequently registered as Green Muscle® in South Africa in 1998. However, the lack of a knock-down action and the slow kill currently makes Green Muscle® unsuitable for operational use in the Karoo. The thousands of individual hopper bands treated during control campaigns, and the high mobility of bands, would make the recognition of treated and untreated targets by locust officers impossible. The hot and dry Karoo climate is also usually detrimental for the survival and transmission of fungal conidia, while the thermoregulation behaviour of brown locust hoppers enables them to effectively delay the onset of Metarhizium mycosis. An alternative application strategy needs to be developed and tested before Green Muscle® can be recommended for brown locust control. Other pathogenic micro-organisms evaluated in the laboratory for brown locust control were certain acid-tolerant strains of Bacillus thuringiensis and an entomopoxvirus isolated from a West African grasshopper, Odaleus senegalensis (De Geer). Unfortunately, none of these microorganisms proved virulent to the brown locust. The alternative locust control methods evaluated against the brown locust were all ranked according to various performance criteria and compared with the conventional spraying of ULV insecticides. Of the alternative control methods, only Adonis® barrier treatments and Regent® bait showed sufficient promise for brown locust control. However, none of the alternatives were considered suitable under all locust control situations to entirely replace the spot spraying of conventional ULV insecticides, which will thus remain the backbone of brown locust control strategy. Recommendations on the development of an lPM strategy for brown locust control, to incorporate barrier treatments and baiting in certain areas of the Karoo in order to complement conventional insecticide spraying, are given.Item Open Access Fish myxosporeans from the Okavango Delta, Botswana and the south coast of South Africa(University of the Free State, 2003-12) Reed, Cecile Catharine; Basson, Linda; Van As, Liesl L.; Dykova, IvaEnglish: Myxozoans form a diverse and economically important group of endoparasites that have been intriguing researchers ever since the early1800's. These parasites are notorious, having been associated with the devastating effects many species have shown in aquaculture and fisheries industries throughout the world. Research on both freshwater and marine myxosporeans in Africa is limited to a few countries and has, until recently, been largely neglected in southern Africa. In recognition of the need to investigate the presence of fi sh-infecting myxosporeans in both the freshwater and marine environments of southern Africa, a study was initiated in 1997 investigating the biodiversity of myxosporeans infecting fi shes in two very unique southern African localities. Firstly, the Okavango River and Delta in Botswana contains one of the worlds largest inland deltas composed of about 18 000 km2 waterways. Situated in the middle of the Kalahari Desert, this pristine wetland is the only one of its kind that forms an inland delta and one of the few river systems in the world that is visible from space. The research on myxosporeans infecting marine fi shes was conducted along the Cape south coast of South Africa, which has one of the most diverse marine fauna and flora compositions in the world of which 13 % is endemic. This study aimed to review all existing literature concerning freshwater and marine fish-infecting myxosporeans in Africa, report on the biodiversity and prevalence of fi sh-infecting myxosporeans in the Okavango River and Delta, Botswana, investigate the pathogenic potential of myxosporeans infecting the Okavango fi shes, determine the taxonomic status, species biodiversity and prevalence of myxosporeans infecting fi shes along the Cape south coast, South Africa and investigate the pathogenic potential of myxosporeans infecting intertidal and surf zone fi shes along the Cape south coast of South Afri ca. The examination of 285 8 fi shes representing 14 families and 65 species on several field trips to the Okavango Ri ver and Delta from 1997 to 2001 revealed the presence of 29 different fish infecting myxosporeans representing the genera Henneguya Thelohan, 1892 and Myxobolus Btitschli, 1882. Six of these species have been described as new in three articles prior to this study. Another two new species have been recorded in this thesis, together with the records of 14 miscellaneous species that have never been described before, but require more materi al for the completion of species descriptions. During the course of nine surveys conducted along the Cape south coast of South Africa since March 1998, a total of 410 fishes representing 33 species were examined for parasitic infections. Results from these surveys revealed the presence of 15 different myxosporean species. Three species from the genus Ceratomyxa Thelohan, 1892, one species from the genus Henneguya, two from the genus Myxidium Biltschli, 1882, one species from the genus Myxobolus and one species from the genus Sphaeromyxa Thelohan, 1892 are described in this thesis. Two keys for the identification of both the freshwater, as well as marine and estuarine fish-infecting myxosporeans in Africa are presented as a conclusion to this study. The results obtained from this study have laid the foundation for the continuation of research on these parasites in southern Africa and has provided an insight into the great diversity of myxosporeans infecting southern African fishes.Item Open Access The influence of clothing, wrapping and physical trauma on carcass decomposition and arthropod succession in central South Africa(University of the Free State, 2006-06) Kelly, Janine Anne; Van der Linde, Theuns C.; Anderson, Gail S.English: Forensic entomology is the study of arthropods associated with bodies. Arthropod successional studies have been successfully used to estimate a postmortem interval. This research was to determine the influence of a) seasons, b) clothing, c) wrapping and d) knife wounds on carcass decomposition and arthropod succession. The experimental site consisted of a 26 hectares grass field interspersed with trees. For the wrapped trials, six pig (Sus scrofa) carcasses were divided into three sample groups, each with a clothed carcass and an unclothed carcass wrapped in sheeting. Arthropod sampling was done (i) daily, (ii) five day intervals and (iii) ten day intervals. Two additional unwrapped carcasses, one with clothes and one without, were sampled daily as controls. For the wounds trials six carcasses were divided into three groups. Each group consisted of a carcass with clothes and one without clothes. The wounds consisted of (i) a knife wound to the throat, (ii) three deep knife wounds, in the back, in the front thoracic and in the front abdominal region. The controls, were without any wounds. Oviposition occurred simultaneously and was not delayed or hastened by the presence of wrapping, clothing or wounds. However, during the winter wrapped trials there was a delay of four days. In winter, the carcasses remained acceptable to Diptera for oviposition over an extended period. Oviposition continued up to two months after placement, whilst in the warmer seasons oviposition occurred within the first few days. The Diptera did not select the wounds as oviposition sites. Calliphoridae and Sacrophagidae were the dominant Diptera recorded during all the trials. In the autumn and summer seasons Chrysomya marginalis and Chrysomya albiceps were the dominant species. In the spring seasons, the dominant species were Chrysomya chloropyga and C. albiceps. In the winter seasons, Sarcophaga cruentata , C. chloropyga, Calliphora vicina, and Lucilia spp. were the species breeding on the carcasses. Muscidae adults were present during all the seasons, but no maggots of this family were recorded. Due to the short oviposition time during warmer seasons, the maggots were of a similar age at any time. Due to the extended oviposition that occurred during winter, different instar groups, often the same species, were present at any time. In all seasons the Coleoptera community present on the carcasses were dominated by Dermestes maculatus (adults and larvae) and Necrobia rufipes. In the summer Thanatophilus micans (adults and larvae) and Histeridae spp. were also recorded on the carcasses. There was no overall difference in arthropod succession between any of the carcasses. During the autumn seasons, noticeable predation by C. albiceps maggots on C. marginalis maggots was observed. There was limited maggot predation during the spring trials and some predation observed during the summer trials. Presence of clothing, wrapping and wounds had no influence the Coleoptera community. In the winter seasons, D. maculatus larvae were found while the maggots were still present on the carcasses. In summer seasons, they were only present after maggot migration. Significant maggot mortality was associated with the wrapped carcasses during the warmer seasons. The presence of the sheets or clothing did allow the maggots to move more freely on the surface of the carcasses, especially in the summer. Less skin remained on the wrapped or clothed carcasses after the maggots migrated to pupate.Item Open Access Parasitoids and aphid resistant plants : prospects for Diuraphis noxia (Kurdjumov) control(University of the Free State, 2007-11-03) Prinsloo, Godfried Jacob; Van Der Linde, T. C. de K.; Van Der Westhuizen, A. J.; Potting, R. P. J.English: Host plant resistance and biological control by means of natural enemies are becoming more favourable as high potential alternatives for chemical control of insect pests. Tritrophic studies (plant–herbivore-natural enemy) indicated that the application of host plant resistance and biological control to a particular pest could give significantly better or worse results than expected from each component respectively. Russian wheat aphid Diuraphis noxia (Kurdjumov) is a serious pest of wheat in South Africa since 1978. Plant resistant cultivars are being used against D. noxia since 1992. The introduction of parasitoids and predators for biological control of this pest automatically led to the development of an integrated pest control programme involving both control strategies. Nothing is known about interactions between resistant cultivars, D. noxia and natural enemies in South Africa. These interactions could have substantial influence on the efficacy of the control programme. The parasitoid Aphelinus hordei (Kurdjumov), introduced from the Ukraine, established in the Lesotho highlands after being released in the wheat production areas of the Free State Province. This parasitoid together with a native parasitoid Diaeretiella rapae (McIntosh), also parasitising D. noxia in South Africa, was included in a study on tritrophic interactions. A. hordei and D. rapae respectively have narrow and wide host ranges. Field studies on the interaction between A. hordei and resistant and susceptible cultivars indicated reduction in aphid population growth on each of the cultivars. Diuraphis noxia was highly parasitised on a susceptible cultivar Betta, while a positive interaction on resistant Gariep occurred, resulting in the enhancement of the resistance. A slightly lower percentage control was found on SST 333 in the presence of A. hordei. Volatile profiles emitted by infested Betta plants and resistant Elands and SST 333 plants, differed qualitatively (different volatiles) and quantitatively (concentration of volatiles). These differences caused behavioural differences between parasitoid species e.g. A. hordei could not distinguish infested from clean Elands, while D. rapae did. Diaeretiella rapae could not distinguish infested from clean SST 333 while A. hordei did. Aphelinus hordei could not distinguish between infested Betta and Elands, while D. rapae significantly preferred Betta to Elands. Parasitoids therefore responded to different volatiles from the same cultivars. This means that both A. hordei and D. rapae, use different volatiles or volatile combinations from the same plant-herbivore combination in host habitat location. Semiochemicals e.g. methyl salicylate, that act as insect behaviour-modifying chemicals, was tested in the laboratory and the field as potential control options against D. noxia. Volatile compounds released by plants could serve as signals attracting beneficial insects and induce a variety of responses in plants. A slow release wax pellet formulation named OX54 releasing methyl salicylate, menthol and 1,8-cineole was tested. Olfactometric studies showed that D. noxia and R. padi was repelled by each of the compounds although not released by their alternate host plants in South Africa. Both parasitoid species were repelled by some of the semiochemicals tested, but differences occurred between the two species. Aphelinus hordei did not respond to 1,8 -cineole, while D. rapae was not responding to menthol indicating that the different parasitoids differ in sensitivity to other semiochemicals. The repellence of the parasitoids by methyl salicylate indicated that these volatiles are not induced by D. noxia when feeding on wheat. Different host range of the parasitoids may be a reason for this reaction. OX54 and methyl salicylate respectively caused a delay in the immigration of D. noxia into resistant cultivar Elands during field trials, but on susceptible Betta an increase in infestation was found. Lower infestation on treated Elands resulted in a slight increase in yield compared to the control. The positive integration of host plant resistance and biological control can have two objectives namely synergistic reduction of pest densities and the protection of durability of resistance. Some resistant wheat cultivars to D. noxia seem to be highly resistant and the efficacy of natural enemies in these wheat fields is of utmost importance. The application of semiochemicals in these cases should also be investigated . Where resistant cultivars are less effective and hence have more durable resistance, the value of biological control is to enhance the effect of plant resistance on the reduction of the pest population in such a way that the effects of plant resistance and biological control are sufficient to prevent damage. The understanding and effective manipulation of agro -ecosystems in the wheat production areas of the Free State Province is therefore essential for the successful establishment of a successful integrated pest control programme.Item Open Access Forensic entomology: the influence of the burning of a body on insect succession and calculation of the postmortem interval(University of the Free State, 2009) Kolver, Jacobus Hendrik; Van der Linde, Theunis C.Forensic entomology is the application of the study of insects and other arthropods which are associated with legal issues and certain suspected criminal events. Successional studies have been successfully applied in criminal cases to determine the postmortem interval (PMI). This research was done to establish the influence of burning on a body’s decomposition, insect succession and calculation of the PMI. Field trials were conducted during different seasons of successive years on the campus of the University of the Free State, Bloemfontein, South Africa. The experimental site where the field experiments were conducted, consists of 24 hectares of open grassveld with a few scattered trees. Four pig (Sus scrofa) carcasses were used during each trial, one carcass as control and three carcasses burnt with different volumes of LRP petrol to a CGS level 2 or 3 burn injury with varying degrees of charring. The carcasses were sampled daily for arthropod activity, carcass mass, decompositional stage and microclimate. The control and SB (slightly burnt) carcasses decomposed at a similar rate during the warmer seasons. During the colder seasons, the SB carcass decomposed faster than the control carcass. The slowest decomposition occurred at the MB (medium burnt) and HB (heavily burnt) carcasses. Burning had an effect on the colonisation of Chrysomya chloropyga, Chrysomya marginalis and Chrysomya albiceps. Oviposition occurred simultaneously at all carcasses (autumn, spring & during heavy rainfall in summer ), at the burnt carcasses one day prior to the control carcass (spring & summer) and at the burnt carcasses three to five days prior to the control carcass (autumn & winter). An exception occurred during a single trial when oviposition occurred at the burnt carcasses five days after oviposition at the control carcass (winter). During the warmer seasons oviposition time was shorter, resulting in maggots of similar age at all of the carcasses. During the colder seasons oviposition time was extended, resulting in maggots of different ages and instars on the same carcass and between carcasses. During all trials, except for the summer trail with heavy prolonged rainfall, only the control carcasses reached the Dry/Remains Stage. The burnt carcasses only reached the Advanced Decomposition Stage during the same timeframe. Calliphoridae were the dominant Diptera during all trials. Dominant Diptera species, in numerical order, were Chrysomya marginalis, Chrysomya albiceps and Chrysomya chloropyga. Muscidae adults were recorded during all trials, but no maggots were observed or collected. Coleoptera were dominated by Dermestes maculatus (adults and larvae) and Necrobia rufipes (adults). Coleoptera dominance increased with the level of burning. Differences in arthropod succession between the carcasses occurred due to the effect of burning on the time of oviposition. The PMI calculated for a burnt body would be one to five days shorter than the PMI for an unburnt body, depending on the extent of bloating of the burnt body, the season and ambient temperature. During warmer months the PMI of a burnt body and an unburnt body would essentially be the same due to simultaneous oviposition. Laboratory trials revealed that feeding on burnt media caused C. chloropyga maggots to reach pupation one day faster than the control. No significant difference was found between the treatments for the development time from pupation until adult eclosion. No significant difference was found between the treatments for the mean total development time for C. chloropyga. A 10.6% higher survival until adulthood was found on the burnt media than the control. Morphometrics revealed a higher pupal mass for the control than the burnt media. No signifant difference was found for the adult dry mass and wing length for the control and the burnt media.Item Open Access Pests and predators on genetically altered cotton (Bt-cotton) and associated host plants in South Africa(University of the Free State, 2009-09-23) Bennett, Annette; Van der Westhuizen, M. C.The efficacy of the Bt-genes (the cry1Ac and cry2Ab2 genes) were evaluated for bollworms (i.e. the American or “African” bollworm, Helicoverpa armigera, the red bollworm Diparopsis castanea and the spiny bollworm species, Earias biplaga and E. insulana) on cotton under normal spraying conditions in different field trials in South Africa. Differences that were found in bollworm efficacy and yields are explained by comparison in various field trials. Bt-cottons (Genetically Modified Cotton) exhibiting either only bollworm resistance (NuOPAL), or cotton exhibiting both bollworm resistance and herbicide tolerance (NuOpal RR)-, or cotton exhibiting only herbicide tolerance (DeltaOpal RR) were compared with non-Bt-cotton (DeltaOPAL). At the same time the effect of the Bt-gene on non-target organisms, such as secondary pests and predator numbers was monitored. Since most of the small-scale farmers in South Africa cultivate Bt-cotton and they are required to plant a refuge as part of a Resistance Management Programme, the abundance of alternative host plants for bollworms was evaluated in the largest small-scale production region, the Makhathini Flats (KwaZulu-Natal). Finally, the acceptance of Bt-technology amongst growers are discussed. This study was undertaken over a number of years and the repetition of a number of the trials at different localities has showed that Bt-technology has proved to be not only effective against the target pests, which are the african bollworms on cotton, but it is also beneficial to farmers in the form of a higher yield production and improved crop protection. The effect of the Bt-gene on non-target organisms is minimal if present and the Bt-gene has no detrimental effect on predator numbers, especially in the presence of an increase in insect host numbers, irrelative of the cotton type planted. The increase in predator numbers and secondary pests is a result of the decrease in the number of bollworm sprays applied on Bt-cottons to control bollworm, as bollworms are effectively controlled by the Bt-gene. In some instances when additional sprays for secondary pests were applied, the benefit for the grower to plant Bt-cottons, is reflected in the higher yields and lower input costs as a result of the absence or fewer bollworm sprays. The host plant study showed that alternative host plant abundance in an area where cotton is cultivated, can provided evidence for a possible alternative refuge to conventional cotton. The fact that very little, of the cotton planted by South African farmers are conventional cotton (non-Bt-cotton) varieties, confirms the acceptance of Bt-technology amongst cotton growers, with full acceptance of the requirements of planting this cotton, while obtaining higher yields per surface area than in the case of non-Bt-cottons. The benefits of planting Bt-cotton that have been illustrated in this study, clearly demonstrates the acceptance of Bt-cotton in South Africa, especially amongst, the commercial and the small-scale farmer, by enabling cotton growers to farm more cost-effectively.Item Open Access Activity patterns of birds in the central Free State, South Africa(University of the Free State, 2009-11) Van Niekerk, Daniël Johan; Kok, O. B.Activity patterns of bird species were studied at Glen Agricultural College within the grassland area of the central Free State, South Africa, during a period of 11 years (July 1997 - July 2008). The study focused on a specific grassland locality where 5-minute checklists were compiled continuously from dawn to dusk at least once a week for a total of 656 days. Data were also collected each minute for selected species. Additional observations in an adjacent tree and shrub dominated drainage line included I-minute checklists compiled during transects over a two-year period (late autumn 2000/1 to mid-autumn 2002/3) as well as surveys from a fixed position from dawn to approximately 70 minutes after sunrise during 2007/8. The central aim of the study was to quantify and explain annual, seasonal and daily activity patterns of all bird species recorded in the study area. This data is summarised in separate species accounts where aspects of the annual cycle, particularly breeding and moulting, were also considered. In addition, the potential influence of rainfall was investigated. The study reveals, for the first time, how the activity patterns of a southern African bird community change through time, and how the amount and timing of rainfall can influence these patterns. In spite of similarities amongst species when daily, seasonal and annual patterns are considered separately, the study also shows that each species is unique when all its data is considered simultaneously. Because activity patterns can have a substantial influence on the detectability of a species, the accuracy and usefulness of surveys aimed at estimating bird numbers is consequently questioned. The study at Glen also shows how activity patterns can be used to help unravel the annual cycle of species in a time and cost effective way.Item Open Access Key diagnostic characteristics of the developmental stages of forensically important calliphoridae and sarcophagidae in central South Africa(University of the Free State, 2011-12-15) Brink, Sonja Lindsey; Van der Linde, Theuns C. de K.; Basson, Linda; Van Wyk, Pieter W. J.English: The first insects attracted to a decomposing body are usually representatives of the Diptera, in particular members of the families Calliphoridae (blow flies) and Sarcophagidae (flesh flies). These flies will deposit their eggs (or often larvae in the case of sarcophagids) on the body, within a few hours after death, depending on environmental conditions. The immature stages will complete their developmental cycle on and around the body. As a consequence, these insects are of great importance in forensic entomology; the main area of application being the determination of the postmortem interval (PMI). One of the key pieces of information needed to calculate the PMI is the correct species identification of the immature stages. The aim of this study was to provide diagnostic descriptions for the immature stages of forensically important calliphorids and sarcophagids in central South Africa. Forensically important calliphorids prevalent in this region are Lucilia cuprina (Wiedemann), Lucilia sericata (Meigen), Chrysomya chloropyga (Wiedemann), Chrysomya marginalis (Wiedemann), Chrysomya albiceps (Wiedemann) and Calliphora vicina Robineau-Desvoidy. The sarcophagid prevalent in the region is Sarcophaga cruentata Meigen. A range of characteristics was evaluated by means of light and scanning electron microscopy and the most pertinent of these were identified for diagnostic purposes. The eggs were evaluated in terms of nine characteristics; six of which were of no diagnostic use, while three could be used to identify some of the species. The eggs of C. chloropyga and C. albiceps were indistinguishable from each other. Twelve features were identified for their possible diagnostic value in larvae. In first instar larvae five of these characteristics were of no diagnostic value, while six were useful to identify some of the species. All species could, however, be identified with the aid of the cephalopharyngeal skeleton. For second instar larvae, four of the characteristics were of no diagnostic use, but seven were useful to identify some of the species. All the species could be identified using the cephalopharyngeal skeleton. In the third instar larvae four characteristics were of no diagnostic use, but by using three other characteristics some of the species could be identified. All the species could be identified by means of five morphological characteristics (labrum, cephalopharyngeal skeleton, posterior spiracles, spiracular plate and anal area). Seven characteristics were identified for their possible diagnostic values in puparia. Five of these characteristics were useful to identify some of the species, but all the species could be identified with the aid of two of the characteristics (frontal field and bubble membrane). The ultimate aim of the study was to construct keys for use during the identification of specimens found at the crime scene. The keys that were constructed not only mapped out the pertinent diagnostic characteristics, but also considered what characteristics could be combined when a specimen was viewed from a specific angle. Since specimens often reach the forensic laboratory in less than optimal condition, it is essential that a wide range of characteristics and keys be available during identification. This will also enable the forensic entomologist to give priority to specimen preparation and the method of observation when rapid analysis is needed or where very few good specimens are available for identification. With these tools (descriptive diagnostic characteristics and keys) the identification of immature stages of calliphorids and sarcophagids found at the crime scene should be an uncomplicated exercise.Item Open Access Ecology, taxonomy and possible life cycles of blood protozoans infecting crag lizards (Pseudocordylus spp.) from the eastern Free State highlands(University of the Free State, 2012-01) Van As, Johann; Smit, Nico; Davies Russell, Angela; Heideman, NeilEnglish: The study of blood parasites of reptiles is a relatively new and unexplored field in South Africa. Therefore, the general aims of this research were to explore the haemoparasite fauna of cordylid lizards, Pseudocordylus melanotus, Pseudocordylus subviridis and Pseudocordylus langi, and especially to search for the definitive hosts and likely vectors of their haemogregarines. Surveys of lizard blood were conducted at various altitudinal gradients on the Sentinel Trail in the escarpment area of the Drakensberg, and at the top of Platberg, near Harrismith, both in the Free State. Five species of haemogregarines were identified, all suspected to belong to the genus Hepatozoon, and none was known from previously published records. These occurred in the blood of P. melanotus, P. langi and P. subviridis from the two disjunct study sites, and mostly were accompanied by other haemoparasites including a saurian malaria, so-called Sauroplasma, and filarial nematodes. Developmental stages of two of the Hepatozoon spp. were documented in the internal organs of P. melanotus and P. subviridis by means of light and confocal microscopy, histology, and transmission electron microscopy. Life stages were also observed in ectoparasitic lizard mites, by means of stained histological sections, and in stained squashes of mites and mosquitoes. Three species of experimentally reared mosquitoes were found to act as likely definitive hosts for Hepatozoon spp. of P. melanotus and P. subviridis, while wild caught Culex (Afroculex) lineata appeared to serve as a definitive host, and therefore possible vector for an Hepatozoon species of P. melanotus at the top of Platberg. A saurian malaria that appeared to have features of two previously described species was recorded in P. melanotus and P. subviridis. New locality records for so-called Sauroplasma and filarial nematodes were also documented for the three species of crag lizards. Some aspects of the fine structure of two haemogregarines, the Plasmodium sp. and so-called Sauroplasma infections were recorded for the first time in the erythrocytes of the Pseudocordylus spp. Differential leucocyte and thrombocyte counts were performed on the three crag lizard species and, with erythrocyte characteristics, compared with those of cordylid lizards in previous studies. Several types of leucocytes were characterized ultrastructurally, as well as by light microscopy, and attempts were made to correlate statistically leucocyte counts, and host and environmental data, with parasite loads. Finally, mites and mosquitoes associated with crag lizards were explored further as possible vectors of lizard haemoparasites, and studied using light and scanning electron microscopy.Item Open Access Advances in the systematics and ecology of African Corinnidae spiders (Arachnida: Araneae), with emphasis on the Castianeirinae(University of the Free State, 2012-01) Haddad, Charles Richard; vdM Louw, Schalk; Dippenaar-Schoeman, AnsieEnglish: The Corinnidae is one of 76 families of spiders (Arachnida: Araneae) presently recognised in the Afrotropical Region. By the end of the last century their taxonomy and systematics had been very poorly studied and no modern revisions existed on the group. At that time, 110 species in 22 genera were known from the region, making it a family with moderate species richness. The description of the new genus Hortipes Bosselaers & Ledoux, 1998 in the family Liocranidae signalled the start of modern systematics studies in that family, and following the transfer of Hortipes to the Corinnidae, of that family by default too. Since that time, 20 taxonomic papers have been published on the Afrotropical Corinnidae and 10 new genera (all endemic to the region) and 164 new species have been described, of which three species form part of the current study (Chapters 7 and 9). Several genera have also been transferred to or from the Corinnidae in those papers. Presently there are 35 genera and more than 270 species known from the region, with the Corinnidae now ranking eighth in species richness in the region. Most of the revisionary work so far has focused on the subfamilies Trachelinae and Phrurolithinae, while the Corinninae sensu lato and Castianeirinae have largely remained neglected. The broad aim of the current study was to focus on the systematics of the latter group, treat the taxonomy of each of the currently known genera, at least in part, and provide a basis for future work on the subfamily. As such, many of the smaller genera in the subfamily were revised in the Afrotropical Region and two new genera were described. The genus Apochinomma Pavesi, 1881, the only described genus of accurate antmimicking castianeirines from the region, is revised and separated into two species groups based on genitalic and abdominal morphology. The type species, A. formicaeforme Pavesi, 1881, is redescribed and three new species are described in the A. formicaeforme species group: A. malkini sp. nov., A. parva sp. nov. and A. tuberculata sp. nov.. Two new species, A. decepta sp. nov. and A. elongata sp. nov., are described in the A. decepta species group, although an additional species only known from juveniles can also be placed in the latter group. Members of the A. formicaeforme species mimic Polyrhachis ants and are mainly arboreal, while members of A. decepta species group are ground- or grass-dwelling and probably mimic ponerine ants. The genus Cambalida Simon, 1909 is revised and three species are transferred from Castianeira Keyserling, 1879 to Cambalida: C. deminuta (Simon, 1909) comb. nov., C. fulvipes (Simon, 1896) comb. nov. and C. loricifera (Simon, 1885) comb. nov.. An additional species is transferred from Brachyphaea Simon, 1895 to Cambalida: C. fagei (Caporiacco, 1939) comb. nov.. All of these species are redescribed, as is Cambalida coriacea Simon, 1909. Two species, Castianeira depygata Strand, 1916 syn. nov. and C. mestrali Lessert, 1921 syn. nov., are considered junior synonyms of C. fulvipes. The type material of the type species of the genus, C. insulana Simon, 1909 from Annobon Island, is lost, and only immature specimens have been subsequently collected from a nearby island. The species is regarded as a nomen dubium until fresh adult material can be collected. A replacement name, Cambalida simoni nom. nov., is proposed for Cambalida fulvipes Simon, 1909, the latter being a secondary junior homonym of Cambalida fulvipes (Simon, 1896) comb. nov.. The type material of C. simoni is also lost and it too is considered a nomen dubium. Five new species are described: C. compressa sp. nov., C. dippenaarae sp. nov., C. griswoldi sp. nov., C. lineata sp. nov. and C. unica sp. nov.. Castianeira Keyserling, 1879 is the largest genus in the Corinnidae with 131 described species, of which 22 are presently known from the Afrotropical Region. There is a very rich undescribed fauna known from the region, and the variable morphology of its component species would suggest it is polyphyletic and should be divided into several genera. For example, six species are misplaced and have been transferred to or synonymised with species in Cambalida or the new genus Copuetta gen. nov.. In the present study, five species are redescribed and illustrated for the first time based on the type material: C. delicatula Simon, 1909, C. formosula Simon, 1909, C. majungae Simon, 1896, C. phaeochroa Simon, 1909 and C. thomensis Simon, 1909. The female holotype of C. bicolor (Simon, 1890) lacks an abdomen and the species is considered a nomen dubium. The types of several Afrotropical species could not be traced as yet and the species should be redescribed, if possible, based on recently collected material from near their type localities. The ground-dwelling genus Copa Simon, 1885 is one of four genera in the Afrotropical Region that have cryptic colouration that bears a resemblance to that of wolf spiders (Lycosidae), hereafter referred to as cryptic lycosiform colouration. The type species of the genus, C. flavoplumosa Simon, 1885, is redescribed and proposed as a senior synonym of C. benina Strand, 1916 syn. nov. and C. benina nigra Lessert, 1933 syn. nov.. This is possibly the most widespread corinnid in the Afrotropical Region albeit that is has not yet been recorded from any of the islands. A new species, C. kei sp. nov., is described from South Africa. Copa agelenina Simon, 1910, originally described from a subadult female from southern Botswana, is considered a nomen dubium. Although the Madagascan fauna was not included in this revision, nearly 30 new species have been distinguished from museum collections, and once that fauna is revised it will provide an exceptional example of island radiation. In a revision of the Afrotropical species of the ant-mimicking genus Corinnomma Karsch, 1880, Apochinomma semiglabrum Simon, 1896 is redescribed from both sexes, and based on these descriptions it is transferred to Corinnomma as C. semiglabrum (Simon, 1896) comb. nov.. A new species, C. lawrencei sp. nov., is described from Mozambique, Tanzania and South Africa. The taxonomic status of C. olivaceum Simon, 1896 is discussed and the first illustrations of the female genitalic structures are presented. Since no fresh material of this species is available and the female holotype is badly faded, it is not thoroughly redescribed. An English translation of Simon’s (1896) Latin description of C. olivaceum is provided with the intention of more accurately describing the colouration of this species. The arboreal cryptic lycosiform castianeirine genus Echinax Deeleman-Reinhold, 2001, previously known only from South-East Asia, is recorded from the Afrotropical Region for the first time. Copa longespina Simon, 1909 is redescribed and the species is transferred to Echinax as E. longespina (Simon, 1909) comb. nov.. Six new species are described from both sexes: E. clara sp. nov., E. hesperis sp. nov., E. natalensis sp. nov., E. scharffi sp. nov., E. similis sp. nov. and E. spatulata sp. nov.. The genus Graptartia Simon, 1896, presently known only from Africa, is revised. The type species, G. granulosa Simon, 1896, is redescribed and the first genitalic sketches of the species are provided. Two new species, G. mutillica sp. nov. and G. tropicalis sp. nov., are described. Unique amongst African castianeirines, all species of Graptartia are mimics of wingless female velvet ants (Mutillidae). Although the genus Merenius Simon, 1909 is not revised, a single common species, Merenius alberti Lessert, 1923, is redescribed. The species was previously known only from South Africa, and is recorded for the first time from Mozambique, Swaziland and Zimbabwe. While most populations of M. alberti comprise the typical black morph of the species, a red morph is described for the first time here. As part of a field study to identify the potential models of the two colour morphs of M. alberti, spiders were collected by hand and ants by pitfall trapping in the Ndumo Game Reserve in northern KwaZulu-Natal, South Africa. The ants assemblages sampled at 20 sites in the reserve seem to indicate that the black morph is a generalised mimic of black ground-dwelling ants, most likely Camponotus cinctellus (Gerstäcker, 1859), Streblognathus peetersi Robertson, 2002 and Polyrhachis gagates F. Smith, 1858, while the red morph is a mimic of Anoplolepis custodiens (F. Smith, 1858) ants. Lastly, the genus Messapus Simon, 1898, presently placed in the Castianeirinae, is reviewed. The type species, M. martini Simon, 1898, clearly represents two different species, one a corinnine (female lectotype) and the other a castianeirine (male paralectotype). The female is redescribed and the true male described for the first time. Based on the redescription, Messapus is transferred to the Corinninae. Corinna natalis Pocock, 1898 is misplaced and is transferred to Messapus as M. natalis (Pocock, 1898) comb. nov., while Messapus secundus Strand, 1907 is misplaced and transferred to Merenius as M. secundus (Strand, 1907) comb. nov.. A new cryptic lycosiform genus, Copuetta gen. nov., with the type species C. maputa sp. nov., is established to accommodate the castianeirine male paralectotype of M. martini, and its matching female is described for the first time. Castianeira kibonotensis Lessert, 1921 syn. nov. is considered a junior synonym of Copa lacustris Strand, 1916 and the species is redescribed and transferred to Copuetta gen. nov. as C. lacustris (Strand, 1916) comb. nov.. An additional eleven new species of Copuetta gen. nov. are described: C. comorica sp. nov., C. erecta sp. nov., C. kakamega sp. nov., C. kwamgumi sp. nov., C. lesnei sp. nov., C. litipo sp. nov., C. lotzi sp. nov., C. magna sp. nov., C. naja sp. nov., C. uzungwa sp. nov. and C. wagneri sp. nov.. A second new cryptic lycosiform genus, Wasaka gen. nov., is described for four new species from tropical Africa: W. imitatrix sp. nov., W. montana sp. nov., W. occulta sp. nov. (type species) and W. ventralis sp. nov.. A phylogenetic analysis of the subfamily Castianeirinae from the Afrotropical Region was carried out. Forty-one ingroup taxa (Castianeirinae) were included, of which 39 were Afrotropical, one Australasian and one Brazilian. Outgroup taxa included three species of Trachelinae, one Phrurolithinae, two Corinninae and two Corinnidae incertae sedis, with Drassodes sesquidentatus Purcell, 1908 used to root the trees. Only species of Castianeirinae treated in this thesis and known from both sexes were included in the analysis. Analyses performed in Winclada, TNT and PAST all produced similar but very unsatisfactory results, with the outgroups grouping together with part of the Castianeirinae. Consequently, a second analysis was conducted with the exclusion of most of the outgroup taxa (except D. sesquidentatus and Corinninae). These results improved the resolution of the results considerably. but still did not resolve the placement of the Medmassa–Messapus clade within Castianeirinae; these genera can be considered to belong to Corinninae and should hypothetically have been placed outside the Castianeirinae clade. A single analysis produced in PAST produced the most parsimonious tree, with Medmassa–Messapus placed outside the Castianeirinae and each of the Afrotropical castianeirine genera as monophyletic. The results are inadequate to support any systematic changes in the Corinnidae, but future analyses need to include a more diverse range of castianeirine genera from outside the Afrotropical Region to better understand the relationships of the Afrotropical fauna. In the final chapter, the role of Castianeirinae as components of arthropod mimicry complexes is described for three species of ants, Anoplolepis custodiens (F. Smith, 1858), Polyrhachis gagates F. Smith, 1858 and Camponotus fulvopilosus (De Geer, 1778). There are respectively two out of 10, four out of six, and zero out of five species of Castianeirinae forming part of the arthropod complexes associated with these ants. All of these castianeirines are inaccurate (weak/ generalised) mimics of their models except for Apochinomma formicaeforme, which is an accurate (good/specialised) mimic of P. gagates. Colour polymorphism is also described for the first time in four species of Afrotropical Castianeirinae, i.e. Corinnomma semiglabrum, Merenius alberti, Castianeira cf. venustula (Pavesi, 1895) and Copa flavoplumosa. Three of these species are inaccurate mimics of ants, while C. flavoplumosa is a species with a widespread variant with cryptic lycosiform colouration and a nigrito form restricted mainly to tropical forests. High Castianeirinae biodiversity and endemism corresponds to most of the main Biodiversity Hotspots and Centres of Endemism (CE) in the Afrotropical Region: Maputaland-Pondoland-Albany CE (five endemics), Madagascar and Indian Ocean Islands CE (>30 endemics), East African Afromontane Forests CE (four endemics), East African Coastal Forests CE (five endemics), Guinean Forests of West Africa CE (seven endemics) and the Horn of Africa CE (one endemic). No endemic castianeirines have been recorded in the Succulent Karoo and Cape Floristic Region CE’s in southern Africa, although this corinnid fauna of these two CE’s is largely dominated by Trachelinae, most of which are endemics.