Observation on some possible attractants of tsetse flies (Glossina morsitans Westw. and G. pallidipes Aust.).

Abstract

Investigations into some possible attractants ofGlossina morsitansWestw. andG. pallidipesAust. 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, andG. pallidipesmay respond to smell more readily thanG. 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 maleG. pallidipesresponded to black light within four hours while withG. morsitansa 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.