Seasonal abundance and diurnal variations in activity of some Stomoxys and Tabanidae in Uganda

Abstract

The results are described of 202 24-hr, catches of Stomoxys and Tabanids on cattle at Lugala on the north-eastern shore of Lake Victoria, and also of six 24-hr, catches at Sukulu, 33 miles from Lugala, all of which were made in 1961–63.Species of Tabanus and Ancala were more abundant in open grassland than inside the edge of the lake-shore forest. Stomoxys nigra, Macq. and S. Calcitrans (L.) were equally numerous in both situations, whereas S. omega Newst. was most abundant inside the forest edge.Many species were caught during all months of the year. In both catching areas, there were seasonal rises in numbers of nearly all species between May and August and again in November or December, that is, towards the end of the rains and early in the dry seasons. At one of the two areas there was also a large increase in catch of a few species in April, in the middle of the main wet season.Diurnal activity of Tabanus and Ancala was greatest near the middle of the day, the exact timing of the peak varying with season. Four species of Haematopota exhibited morning and evening peaks with lower activity at midday, and a rather rare fifth species was apparently more active in the middle of the day. Three species of Stomoxys were also most active in the morning and late evening, but peak activity of a fourth species, S. calcitrans, occurred shortly after midday. Activity during the night was rare.