Populations of adults of Smicronyx guineanus Voss and Smicronyx umbrinus Hustache were sampled on the witchweed Striga hermonthica (Del.) Benth, in Burkina Faso. Samples were taken at four localities in 1991 and at one locality in 1992 and 1993 using a Univac portable suction sampler, beginning at emergence time of the adult weevils, to assess their dispersion patterns and the optimum sample size for Smicronyx. Sampling was done weekly by placing the 60-mm-diameter suction cone on a Striga plant until it was about 5 cm above the ground. Smicronyx adults on S. hermonthica were aggregated. A sample size of 20 and 126 units provided a 25 and 10% precision level respectively at six Smicronyx adults per sampling unit. A chart was designed which could be useful for determining the level of precision attainable at various densities of Smicronyx adults for sampling and monitoring programmes. Larval vertical distribution of Smicronyx was described. Striga plants were stratified with respect to distance from the base and categories were designated as upper, central and lower parts. Results indicated that Smicronyx larvae were located in the upper stratum of the witchweed where they made galls and destroyed large numbers of seeds.

Studies on the vertical distribution of phlebotomine sandflies were carried out at Marigat (Kenya) at determined heights above ground level in both wooded and open fields. Traps set up at different heights from 0–11 m (in wooded area) and 0–9 m (in open field), showed a clear vertical zonation of sandflies as large numbers were collected between 0–7 m in the first site and 0–4 m in the second ones. Among the nine sandfly species collected, Sergentomyia bedfordi Newstead and S. antennatus Newstead were the only species recorded at a height of 11 m above the ground and the commonest sandflies at all studied heights. Overall, more sandflies were collected from the wooded area than the open field. The relationships between the sandfly relative abundance and their heights of flight above the ground showed significant negative correlation coefficients.