Bulletin of Entomological Research (1999) 89, 255–261 255 Development of odour-baited traps for Glossina swynnertoni (Diptera: Glossinidae) P.N. Ndegwa* and S. Mihok International Centre of Insect Physiology and Ecology, PO Box 30772, Nairobi, Kenya Abstract Three new prototype traps, (S1–S3), were developed during studies of the behavioural ecology of Glossina swynnertoni Austen in Kenya and Tanzania. The traps were compared in latin square experiments relative to the regular biconical trap as a standard and a selection of other conventional tsetse traps. Observations were also made on fly behaviour in the vicinity of traps using electric nets and sticky materials. When baited with acetone and 1-octen-3-ol, the S1 trap was 3.5 times as effective in catching G. swynnertoni in Kenya as the biconical trap. In Tanzania, the relative performance of the S1 and biconical traps differed; also, both traps were found to be inferior to an all-black, sticky 1-m 2 target. A second prototype (S2) performed slightly better than the biconical trap, but was still inferior to the black target. The final prototype (S3) was 2.9 times as effective as the biconical trap and performed as well as the black target. The potential for further improvement of traps for capturing G. swynnertoni and flies of the G. morsitans Westwood group is discussed. Introduction The morsitans group of tsetse flies (Glossina spp. (Diptera: Glossinidae)) are important vectors of animal trypanosomia- sis in the productive savannahs of Africa where large numbers of pastoralists graze their livestock. In the past decade, considerable advances have been made in the sampling and control of savannah tsetse through the use of artificial bait technology. This technology combines a visually attractive killing device, e.g. a mechanical trap or an insecticide-impregnated cloth target, with olfactory attractants that together mimic a natural host (Vale, 1993; Green, 1994). In the sole case of G. pallidipes Austen (Diptera: Glossinidae), effective traps have been developed (Brightwell et al., 1991) and are being deployed on a large scale with success (Brightwell et al., 1997). For other savannah tsetse, including G. swynnertoni Austen, there are no truly effective traps; hence, control has relied on the use of insecticide-impregnated targets or, more recently, live baits (Green, 1994). Blue/black or all-black targets, with or without flanking panels of netting, have been used to control G. m. submorsitans Newstead (Filledier & Politzar, 1985; Mérot & Filledier, 1985; Leak, 1996), G. m. centralis Machado (Willemse, 1991; Knols et al., 1993), G. m. morsitans Westwood (Vale et al., 1988; Vale, 1993) and G. swynnertoni (TPRI, 1994) in both pilot trials and large-scale operations. Aside from the problem of control, detection and monitoring of members of the morsitans group, particularly at low population density, has been constrained by the lack of effective traps. The main problem compounding trap development has been the tendency of morsitans tsetse to circle rather than alight on artificial objects (Hargrove, 1976, 1980a; Green, 1993). The stimuli presented by artificial objects are still far from ideal, with considerable room for improvement. A typical example is G. m. morsitans which rarely lands on artificial stationary objects (and hence enters traps) in the absence of appropriate host odour cues, particularly carbon dioxide (Vale & Hall, 1985a,b). Studies on G. m. morsitans have provided most of the information available on both close- and long-range, trap- orientated behaviour of flies in the morsitans complex (Green, 1993). These studies have shown that careful manipulation of size, shape and colour can enhance the visual attractiveness of artificial objects, as well as landing behaviour (Hargrove, 1980a; Vale, 1982; Green, 1986; Green *Fax: 254 2 445763