158 



BIBIONID^E. 



respects to that of the LEPTID^E, among the BKACHYCERA, but the 

 very different venation and antennae, and the form of the anal 

 cell (wider at the distal end than at the proximal) will at once 

 indicate that they belong to the NEMATOCERA. They are practically 

 world-wide in their distribution, a good number of them being 

 vernal or autumnal in their appearance. 



Fig. 16. 



, Meij. ; a, antenna ; b, fore leg ; c, hind leg. 



Head generally much flattened, in Bibio conspicuously so, some- 

 times appearing more nearly horizontal than perpendicular. Eyes 

 rounded or reniform, irrespective of sex ; the upper facets in the 

 male much larger than the lower ones, the two kinds sharply 

 demarcated. Eyes in male very large, often occupying nearly the 

 whole of the head ; contiguous or practically so ; in many species 

 densely pubescent. In the female, the eyes are much smaller, 

 wide apart, the frons sometimes being half the entire width of 

 the head, sparsely hairy only, or bare. Three distinct ocelli 

 present, closely contiguous in Bibio, in the shape of a triangle, 

 the space on which they are placed, the " ocellar triangle," often 

 much elevated above the level of the (contiguous) eyes (male), or 

 frons (female). Proboscis short, blunt, with thick pubescent 

 lamellae ; palpi variable, 4- or 5-jointed, long or short. Antenna 

 of eight to twelve joints ; scape slightly but distinctly differen- 

 tiated ; flagellum of rather closely applied bead-like joints, the last 

 one conical. 



Thorax highly arched, generally closely pubescent. In Dilophus, 

 armed on the dorsum with two peculiar transverse rows of strong 

 teeth-like spines. Scutellum semicircular; metanotum fairly 

 obvious. 



Abdomen a little longer than the body, of seven or eight seg- 

 ments, broadly conical, sides sometimes nearly parallel. Genital 

 organs of male consisting of a well-developed pair of two-jointed 

 claspers, the 2nd joint rather smaller and shorter, generally more 



