The bio-ecology and control of Coproica vagans and Coproica hirtula (diptera: Sphaeroceridae) in cattle feedlots

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.