Further Studies of the Food of Tsetse Flies

Abstract

In an earlier paper we reported identifications of the gut contents of gorged Glossina swynnertoni Austen and G. pallidipes Austen throughout a year in an area where G. swynnertoni was the more abundant species (Glasgow, Isherwood, Lee-Jones & Weitz 1958). Suidae (warthog and bushpig) were the origin of 76-90o% of the feeds of G. swynnertoni and of 94 % of the feeds of G. pallidipes. We report here a somewhat similar study from another area where G. pallidipes is abundant, G. brevipalpis Newstead is found rarely and G. swynnertoni is absent. Collections continued over 9 months. They were made in a systematic manner on a line transect, and records were kept of the place in which each gorged fly was caught. Unfortunately the resources at our disposal did not permit a correspondingly close study of the distribution of the host animals. Nevertheless differences in the hosts used are seen to be related to the places in which the flies were found. PROCEDURES The investigation was conducted in an area of evergreen thicket called Ruma (0? 36' S., 340 19' E.) in the Lambwe Valley in the South Nyanza District of Kenya. Some botanical detail is given by Ivens & Cochrane (1956). Here we need note only the existence of three vegetational phases (Fig. 1.) In the first, believed to be the youngest, dense thicket clumps some 10 yd across are so abundant as to cover 50% of the area, the intervening spaces being grassed. In the second phase the clumps have apparently expanded to cover the whole area. This formation is 15-25 ft high; it contains many species of trees, shrubs and creepers of which none is obviously dominant, and is known to botanists as dense secondary dry forest. In the third phase the candelabrum Euphorbia bilocularis N. E. Br., which was frequent in the dense secondary dry forest, becomes dominant. The thick succulent branches interlace to form a dense canopy at about 30 ft, the shade of which suppresses almost all the undergrowth. The candelabrum forest is the only part of Ruma where free movement, other than along previously prepared paths, is possible.