Effect of weather conditions on the flight activity of Nigerian blackflies (Diptera: Simuliidae)

A vehicle-mounted net was used to make hourly catches of blackflies at 700-1000 m altitude in the River Assob valley, central Nigeria, on 20 days during the dry season. Pearson Correlation Matrix analysis of the collection data and meteorology showed that the main factors affecting flight activity of each of the four most abundant blackfly species were primarily light intensity and secondly wind velocity, whereas relative humidity was the least important factor. Flight activity showed a negative linear regression against wind, with some activity occurring in wind speeds up to 15 km/h. Distance-weighted least-squares (DWLS) regressions showed little correlation of temperature with activity for Simulium hargreavesi and S.adersi, but S.squamosum and S.vorax had small peaks at 28°C and 31°C, respectively. DWLS regression against light intensity showed an activity peak at 6000 lux, except in Simulium adersi.