Van Pletzen, R.Hewitt, P. H.Van der Linde, Theunis Christiaan De Klerk2017-04-262017-04-261984-01http://hdl.handle.net/11660/6165English: 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.Afrikaans: Aangesien min bekend is aangaande die voorkoms, verspreiding en moontlike vektorrolle van muskiete in die westelike Oranje-Vrystaat, is besluit om die spesieverskeidenheid, volopheid en seisoenale fluktuasies van muskiete in hierdie gebied te bepaal d.m.v. lokvalopnames. Weeklikse versameling van muskiete is vir drie jaar vanaf 1976 - 1978 op die plaas Daniëlskuil, 30 km wes van Bloemfontein, gedoen. In hierdie versameling is verteenwoordigers van 25 spesies teëgekom, waarvan agt vir die eerste keer in die Oranje-Vrystaat gerapporteer is. Culex (Culex) theileri Theobald was die dominantste spesie en het 55,44% van die totale vangs uitgemaak. Weerkundige parameters soos lugtemperatuur, watertemperatuur, relatiewe humiditeit en reënval is voortdurend gemonitor. Met behulp van hierdie klimatologiese veranderlikes is gepoog om die volopheid van die sewe dominante spesies nl. Aedes caballus, Ae. juppi, Ae. lineatopennis, Ae. durbanensis-groep, Anopheles squamosus, Cx. theileri en Cx. univittatus te verklaar en is tot die slotsom gekom dat temperatuur en versadigingstekort die belangrikste parameters is. 'n Cx. theileri-kolonie is in die laboratorium gevestig. Veldwaarnemings en laboratoriumeksperimente het gelei tot die vasstelling van die volgende telingsprosedure en omgewingstoestande: Volwasse individue is by 27°C en 65% relatiewe humiditeit aangehou met 'n dag-nagsiklus van 12 uur lig en 12 uur donkerte, wat een uur oggend- en een uur aandskemering ingesluit het. Voeding het bestaan uit 7,5% suikerwater en duifbloed as bron van proteïene. Optimum eierlegging het plaasgevind in lêbuisies met 10 ml teelpanwater in. Larwale ontwikkeling het in 0,02 M NaCl by 27°C in teelpanne in die teelkamers plaasgevind. Die larwes is gevoed met n mengsel van brouersgis en babagraankos. 'n Elektronmikroskopiese ondersoek van die oppervlakstruktuur van die eiers is gedoen. Op grond van die struktuur van die eksochorion kan die eiers hoofsaaklik in vier streke ingedeel word nl. 'n voorste pool, oorgangsgebied, aanhegtingsgebied en agterste pool. Op die voorste pool kom 'n koppievormige korolla voor, gevul met 'n gelatienagtige stof en op die agterste pool 'n oliedruppel. Die knoppies van die aanhegtingsgebied is so gevorm dat knoppies van naasliggende eiers soos drukknopies inmekaar pas en sodoende die eiers aanmekaar hou om n eierpakkie te vorm. Paring kan geskied voor of na bloedinname sonder betekenisvolle invloed op eierproduksie. Suikervoeding na bloedinname het die eierpakkieproduksie nadelig beinvloed, maar nie die aantal eiers per eierpakkie nie. Soogdierbloed (witrotte) het eierproduksie aansienlik laat toeneem, maar die bloed van mannetjie rotte het baie nie-lewensvatbare eiers tot gevolg gehad. Hoewel veroudering van die wyfies eierproduksie laat afneem, het herhaaldelike eierlegging geen afname in eierproduksie of lewensvatbaarheid van die eiers getoon nie. Wyfies lê eiers gedurende die aandskemering. Hulle verkies water met 'n molariteit van tussen 0,01 en 0,08 M NaCl met n donker agtergrond. Oplossings waarin larwes of papies ontwikkel het, of wat bakterieë bevat, is selfs meer stimulerend vir eierlegging gevind. Indien hulle geen keuse gebied word nie, lê hulle op die beskik'bare water . Hoewel temperature onderkant 15°C en bokant 33 °C oögenese nadelig beinvloed, het hierdie temperature geen invloed by die keuse van n geskikte eierleggingshabitat nie. Tydens embrionale ontwikkeling is die eiers nie besonder temperatuurgevoelig nie, maar onderkant 12°C en bokant 36°C vind geen uitbroeiing plaas nie. Die optimum embrionale ontwikkelingstemperatuur was 27°C. Indien die molariteit van die broeihabitat bokant 0,08 M NaCl styg, daal die gemiddelde persentasie uitbroeiing. Bokant 0,16 M vind geen uitbroeiing plaas nie. Temperature van 12°C en 36°C was dodelik vir die ontwikkelende larwes, terwyloptimum ontwikkeling by 27°C voorgekom het. n Styging in die molariteite het nie die ontwikkelingstempo van die larwes baie vertraag nie, maar bokant 0,06M het die mortaliteit van die larwes vinnig begin toeneem. 'n Direkte korrelasie is vasgestel tussen oorlewing van die volwassenes, temperatuur en versadigingstekort. Suiker- en bloedgevoede wyfies het die beste oorlewing getoon by temperature van 6°C - 24°C en versadigingstekorte van 0,4 en 0,8 kPa. Met behulp van die inligting ingesamel tydens veldwaarnemings en laboratoriumeksperimente is gepoog om die voorkoms, volopheid en verspreiding van Cx. theileri te voorspel.afMosquitoes -- South Africa -- BloemfonteinThesis (Ph.D. (Zoology and Entomology))--University of the Free State, 1984ThesisUniversity of the Free State