134 ENTOMOLOGY FOR MEDICAL OFFICERS 



Family Tabanid^ ; Gadflies, Cleggs, Seroot-flies. (Lat. 

 Tabanus = a gadfly). 



The flies of this large family are commonly of stout 

 build and large size, seldom very small. The big head is 

 in the male almost wholly formed by the eyes, which meet 

 across the crown ; in the female also the eyes are large, but a 

 narrow space is left between them, which generally bears a 

 shiny streak or spot, known as the callus. In life the eyes 

 are finely coloured, or iridescent, and marked with purple or 

 brown bands or spots. The antennae consist of 3 segments, 

 the 3rd of which is composed of 4 to 8 subsegments incom- 

 pletely fused together. The mouth-parts (Fig. 38) are 



mand. 

 ^'•■hypoph. 



Pig. 38.— Mouth-parts of Tabanus. 



formed for stabbing and cutting; as a rule the labium is 

 coarse and fleshy and the labella are large, the epipharynx 

 and hypopharynx are dagger-shaped — the one being ventrally 

 grooved, the other cannulate — the mandibles have the form 

 of lancets, and the maxillae are distally serrated. The 

 maxillary palps, which are stiffly pendent on either side of 

 the proboscis, consist of 2 segments, of which the 2nd 

 is often large and tumid. The thorax and abdomen are 

 clothed with short hair and are often rather soberly striped 

 or banded or symmetrically marked. The abdomen is 

 composed of 7 visible segments. The legs are stout, the 

 pulvilli and empodium are large membranous plates. The 

 wing-venation is shown in Fig. 6 ; the 3rd and 4th longitudinal 



