39 



habits, the males of Tabanidae are comparatively seldom caught, 

 with the result that the majority of Tropical species have been 

 described from the female alone ; in the case of Tabanus biguttatus, 

 Wied. (Plate VI., figs. 44, 45), however, males are for some reason 

 encountered much more frequently than usual.* 



No observations as to enemies of Tabanidae appear yet to have 

 been made in Africa, though in other countries these insects are 

 sometimes preyed upon by Robber-flies (Asilidae), as also by 

 fossorial Wasps belonging to the family Bembecidae ; in the United 

 States of America, as well as in Europe, parasitic Hymenoptera of 

 the genus Phanurus have been bred from egg-masses of species of 

 Tabanus. 



Although Tabanus biguttatus, Wied., is the 



Life-history, only African species of which the metamorphoses 

 have yet been studied, f observations made 

 elsewhere upon the life-history of species of Chrysops, Tabanus, and 

 Hcematopota show that in their different stages species belonging 

 to these genera closely resemble one another in their various 

 details ; and, in view of the uniformity in structure and habits of 

 the perfect insects of this family throughout the world, it is not 

 likely that the preliminary stages of African species of the genera 

 mentioned are in any way exceptional. The metamorphoses of no 

 species of Pangonia (sens, lat.) have yet been observed. 



The spindle-shaped, white, brown, or black eggs of Tabanidae 

 are deposited closely packed in sub-conical, rounded, or flattened 

 masses, attached to the leaves and stems of plants, or " other 

 smooth surfaces," projecting from or overhanging water, or standing 

 in wet or marshy ground. The larvae are cylindrical and tapering 

 at each extremity, shining and glassy and more or less longitudinally 

 striated, with a small retractile head, and a body consisting of 

 eleven segments. In colour they are whitish, greyish or yellowish, 

 often with darker markings. Of the eight abdominal segments, 

 each of the first seven is encircled near its anterior margin with 

 a ring of fleshy protuberances or false feet, consisting of a transverse 



* See p. 86. t G f- PP- 89 ' 90 - 



