Research into the relative importance of Tabanidae (Diptera) in mechanical disease transmission. I. The seasonal occurrence and relative abundance of Tabanidae in a Dar es Salaam dairy farm

Data are given on the seasonal occurrence and relative abundance of various species of Tabanids on a dairy farm to the south of Dar es Salaam, Tanzania. Catches of flies resting on the pens were made for 3 h in the morning after the cattle had returned from grazing and were repeated weekly for one year and then monthly for the next two years. The 13 485 female Tabanids taken in the 3 years represented 4 genera and 12 species. Tabanus fraternus Macq. made up 58.4% of this total and T. taeniola P. de B. 24.5%, and these species were considered to be of major concern as possible mechanical vectors of disease agents. T. gratus Lw., T. biguttatus Wied. and Haematopota decora Wlk. made up 6.8%, 5.8% and 3.5% of the total, respectively, and another 7 species together represented 0.98%. The flies were most active during dry, sunny weather. T. fraternus was seen throughout the year. The typical form of T. taeniola could be caught every day in small numbers for most of the year, but there were very great increases in numbers at the beginning and after the long rains, and at these times it was the most abundant species.