The night resting sites of Glossina palpalis palpalis (R.-D.) were observed in a riverine swamp at Bara, Bauchi Emirate, northern Nigeria. The flies were marked with an ultra violet reflecting paint and released at dusk. They were detected with the aid of an ultra violet light beam. Most of the flies (72%) rest on leaves (50% on the upper sides) and on small twigs and creepers (202%). The average resting height was highest in the mid-rains (3-78 m), dropped in the late rains (2-95 m) and was lowest (1-52 m) in the dry season.The resting site heights ranged from ground level up to 18 m. Females were found to rest slightly higher than males and when the moon shone both sexes had a tendency to perch higher. It was shown that the night resting behaviour of G. palpalis is favourable to the application of residual insecticide deposits from the air because most of the spray drops are deposited on leaves.

The technique of applying persistent insecticides (largely dieldrin or endosulfan) from the air by helicopter against Glossina spp. in northern Nigeria is described. In the Guinea savanna vegetation zone, a high degree of discrimination was practised. Where the riverine species G. tachinoides Westw. and G. palpalis palpalis (R.-D.) only were present, spraying was confined to the fringing forest vegetation along drainage lines and in flood plains. Where the savanna species G. morsitans submorsitans Newst. was also present, Isoberlinia woodlands were also sprayed in swaths along the outside edges and penetrating swaths at maximum intervals of 200 m; the denser vegetation encircling the many flat-topped hills was also sprayed, as well as the main tracks and cattle routes. The more undifferentiated woodlands in the southern Guinea savanna zone were sprayed as a grid with swaths at intervals of 150 to 200 m. The degree of discrimination varied according to the fly species and density of the vegetation; usually 5 to 16% of the totally infested area was actually sprayed. So far, approximately 10 000 km 2 have been reclaimed from tsetse by this technique. The degree of reinvasion encountered per annum was approximately 25% of each project area. All reinfested areas have been successfully resprayed. Costs averaged approximately 18 Naira/ha actually sprayed or 2 Naira/ha of reclaimed area in the northern Guinea savanna zone. In the southern Guinea savanna zone, the reclaimed area averaged 3 Naira/ha. The ultra-low-volume spraying technique was introduced in 1972, and this has gradually replaced the conventional spraying technique using emulsion concentrates and booms and nozzles. The ULVA-Bals single-disc atomisers were modified and improved so that droplet sizes within a range of 70 to 200 ju,m volume median diameter can be produced as required. Many insecticide have been tested in the laboratory, preliminary tests on permethrin indicate; that it may prove to be a useful alternative to dieldrin and endosulfan.

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Two years of field trials in Nigeria with the synthetic pyrethroids permethrin, cypermethrin and decamethrin against Glossina palpalis (R.-D.) and G. tachinoides Westw. are described. Laboratory tests were also made against G. morsitans submorsitans Newst. The three pyrethroids were applied successfully from the ground at 0-5%, 0-3% and 0-075 %, respectively, to fly resting sites on vegetation using pressurised knapsack sprayers, populations of both species being eradicated after a single application of one insecticide. Following residual spraying from a helicopter, only decamethrin at 30 g/ha achieved complete eradication. It was thought that, with permethrin wettable powder at 200 g/ha, by modifying the spraying equipment and, with cypermethrin, by increasing the dosage to over 150 g/ha, both could be successful in the future. A new ' sideways' spraying technique tested using the helicopter gave promising results. Comparatively little harm was done to non-target organisms in the environment after spraying with any of the three pyrethroids, and it is expected that they may gradually replace the chlorinated hydrocarbons in future routine anti-tsetse operations.

Catches of Glossina palpalis palpalis (R.-D.) and G. tachinoides Westw. at high and low densities with hand-nets, biconical traps and an electric back-pack trap in Nigeria indicate that 'both types of trap are inferior to hand catching for routine checks of G. palpalis and G. tachinoides populations. Hand catching is recommended as being most suitable for large-scale surveys, assessment of control following insecticide spraying and classical fly-rounds. The biconical trap is recommended for use in experiments of a limited size, monitoring of fly populations on livestock ranches and around Villages, and for capturing flies for dissection. The electric trap is recommended for use in sampling flies in areas of medium and high density and possibly for blood-meal identification. Some blood-meals of G. palpalis were identified.