BIBIONIDTE. 37 



10. BIBIONID^. 



Moderately slender flies, of from three to ten millimeters in 

 length. Head usually somewhat flattened ; front in the male 

 very narrow, or the eyes contiguous ; face short ; eyes round 

 or reniform, often densely hairy in the male ; ocelli large, 

 distinct. Antennae with from nine to twelve joints, cylindri- 

 cal, not longer than the head and thorax together, the joints 

 closely united. Proboscis not long, with thickened, hairy 

 labella; palpi variable, sometimes long, with four or five dis- 

 tinct joints, at other times short. Thorax without suture ; 

 scutellum half round. Abdomen composed of seven or eight 

 segments, not short. Legs moderately long and strong, the 

 hind pair more or less elongated, the front femora thickened ; 

 front tibite usually with a. stout hook or coronet of spines at 

 the tip ; pulvilli and empodium distinct, the latter often pul- 

 villiform. Wings large, the anterior veins stouter than the 

 posterior ones ; costa not extending on the posterior margin ; 

 second longitudinal vein wanting, the third arising from the 

 first ; third vein sometimes furcate ; fourth usually furcate ; 

 first basal and sometimes the second basal cell jjresent ; no 

 discal cell. 



This family comprises about three hundred described species 

 and is of wide distribution. The larvae are cylindrical, foot- 

 less, with transverse rows of bristles, iisually with eyes ; they 

 feed on excremental or vegetable substances, especially on the 

 roots of grass. The pupae are inactive, mostly free, living 

 in excavated, smooth, oval cavities near the surface of the 

 ground, which the larvte have prepared before undergoing 

 their metamorphosis, and wliere the pupae remain before 

 emerging in the perfect form. In some species the males 

 differ very markedly in coloration from the females, so much 

 so that they are commonly mistaken for different species ; 

 they are easily distinguished for their very large eyes which 

 comprise nearly tlie whole head and are covered with hairs. 

 One of the most conimoii s])ecies is l!il>i(> fil/ii'jii'niiis wliich 



