Implementation of the sterile insect technique for tsetse (Glossina spp.) requires that only sterile male insects be released; thus, at some stage of the fly production process the females have to be removed. A further constraint in the use of the sterile insect technique for tsetse is that the females are needed for colony production and hence, a non-destructive method of sex separation is required. In most tsetse sterile insect technique programmes thus far, females have been eliminated from the released material by hand-separation of chilled adults. Using near-infrared (NIR) spectroscopy, significant differences have been found between the spectra for the pupae of male and female G. pallidipes Austen. Significantly, the differences appear to be maximized 4–5 days before emergence of the adults. Tsetse fly pupae up to five days before emergence can be sexed with accuracies that generally range from 80 to 100%. This system, when refined, will enable effective separation of male and female pupae to be carried out, with emerged females being returned to the colony and males being irradiated and released. If separation can be achieved five days before emergence, this will also enable irradiated male pupae to be shipped to other destinations as required. Other Diptera were evaluated using this system but had lower classification accuracies of 50–74%. This may be due to the difference in reproductive physiology between these different fly groups.

Preponderance of Musca spp. and their accessibility to goat feeds and faeces containing Eimeria oocysts prompted an investigation into the role of these flies in the dissemination and/or transmission of goat eoccidiosis. Seventy per cent of the dissected 300 Musca spp. caught in the goat pens where faeces containing Eimeria oocysts were widely scattered, possessed the oocysts in their digestive organs, with the highest number found in the gut. When Musca spp. were induced to feed on faecal solution containing Eimeria oocysts, oocysts were recovered from the flies through regurgitation during subsequent feeding on glucose solution. At low concentrations of 300 and 500 oocysts per g faeces, substantial numbers of oocysts were recovered from the flies only up to 1/2 hr after feeding on the infected faeces; at higher concentrations, oocysts were recovered up to 2 hr. Results of other experiments also showed that the nurriber of flies in which oocysts were found and the number of oocysts recovered were highest when the flies were dissected immediately and 1/2 hr after exposure to infected faeces. The circumstances under which Musca spp, could sustain eoccidiosis and coccidiosis in a goat herd are discussed.