VIII. FAMILY BIBIONID^. 



Fig. 41. Bibio albipennis, enlarged. After Washburii. 



Moderately or very slender flies, of from one to twelve 

 millimeters in length. Head usually somewhat flattened; 

 front in the male usually very narrow or the eyes con- 

 tiguous ; face short; eyes round or reniform ; ocelli large, 

 distinct ('absent in Hesperodes' ) . Antennae composed of 

 from eight to sixteen joints, cylindrical or a little flat- 

 tened, rarely longer than head and thorax, the joints 

 usually closely united. Proboscis never much elongated, 

 with thickened, hairy labella; palpi variable, three to 

 five-jointed, sometimes long, at other times short. Tho- 

 rax without suture; scutellum half round. Abdomen 

 composed of from seven to nine segments, sometimes 

 elongated. Legs moderately long and strong, the hind 

 pair more or less elongated, the front femora often thick- 

 ened; front tibia often with a stout hook or coronet of 

 spines at the tip ; pulvilli and empodium usually distinct, 

 but the former in many of the smaller forms wanting. 

 Wings large, the anterior veins often stouter than the pos- 

 terior ones; costa not extending on the posterior margin ; 



140 



