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Laboratory and field investigations into sex attraction and mating behaviour ofGlossina morsitans orientalisVanderplank have been described. Male flies were not attracted to volatile and soluble compounds from two- to three-day-old mature virgin females, or to virgin females in a simple olfactometer. Removal of antennae from either sex did not appreciably reduce insemination rates after 24–48-h mating periods compared with normal flies. Similar numbers of wild male flies were caught off oxen baited or non-baited with mature virgin females.G. m. orientalisprobably does not produce a pheromone.Male flies appeared to be sexually activated only after movement by the female. Mating success was reduced in the dark and when the male's eyes were painted, but blinding the female fly did not reduce insemination. Mating was similar with or without wings and halteres and the sounds produced by them.Time between pairing the sexes and the start of mating tended to increase, and the percentage of inseminated females accepting two or more matings decreased, after the first copulation. Female flies rarely re-mated within a day. Virgin female flies accepted males passively with partly open wings, and mated females rejected further copulation with closed wings, activity to shake the male off, and primarily a downward-curved abdomen. Virgin female flies mated for periods of 1–45 min did not receive sperm but successfulad libitummating was reduced a day later. Insemination rates decreased with females older than seven days and reached zero 28–83 days after eclosion, while 37-day-old males inseminated 93% of young females.

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Investigations into some possible attractants of Glossina morsitans Westw. and G. pallidipes Aust. have been described. In small cages (8x8x11 in.) under laboratory conditions, flies with painted eyes survived longer than those that were untreated, whilst removing the antennae decreased longevity. Olfactory stimuli were probably more important than vision in orientating a fly towards a static guinea-pig used as a host in a moulded mesh insert into the cage. Field observations indicated that tsetse flies were orientated towards an ox at a distance mainly by vision and few flies found oxen concealed by screens. Olfaction may be used at relatively short distances to find hidden host animals, and G. pallidipes may respond to smell more readily than G. morsitans.Tests in the laboratory and small field cages (6 ft3) indicated that tsetse were not attracted to any particular colour (red, yellow, blue) or shade (white, grey, black). However, in the field more flies were caught off a dark ox than a white ox. In the laboratory > 80% of male G. pallidipes responded to black light within four hours while with G. morsitans a similar proportion was attracted only after six hours. Responses by both species decreased with blue, red and white light and were least with yellow. In small field cages attraction to black light was reduced and only 20–38·6% of either species were caught by a “flap trap” in 6–13½-h test periods. Tests with either blue or red lights in these field cages trapped less than 9% of the released tsetse flies in similar periods. Field trials with black light indicated that this attractant was ineffective as a sampling technique since very few of a natural population were trapped.