HOW TO KNOW THE IMMATURE INSECTS 



8a. Larvae with rudimentary abdominal spiracles; mouth with a large 

 articulated process on each side which bears a nimiber of long 

 hairs and closes, fan-like, when at rest; posterior abdominal seg- 

 ments dilated, the last one armed on venter with a sucker-like disc 

 which bears concentric series of bristles; aquatic species. 

 Fig. 539 Family SIMULIIDAE 



About 300 species of buffalo gnats or black 

 flies are described. The larvae live mostly in 

 swift fresh water and congregate in masses on 

 their webs on rocks in water. The larvae are 

 often so abundant as to completely cover the 

 rocks to which they are attached. The female 

 bites and causes painful swellings. They are 

 disease carriers. 



Simulium 

 pictipes Hagen; b, S. 

 venusfum Say; c, S. 

 sp. (Utah Agr. Exp. 

 Sta.) 



8b. Larvae with distinct though sometimes small abdominal spiracles; 

 mouth without fan-like processes; posterior abdominal segments 

 not noticeably dilated, the last one without sucker-like disc; ter- 

 restrial species 9 



9a. Antennae elongate; body armed with conspicuous bristles or 

 hairs 10 



9b. Antennae usually short and inconspicuous, sometimes apparently 

 absent; body without conspicuous bristles. 

 Fig. 540 Family MYCETOPHILIDAE 



Around 2,000 species of the fun- 

 gus gnats have been described. 

 The larvae inhabit damp places 

 in large numbers. They are active 

 and able to leap. Their food is 

 decaying vegetation and fungi. 

 Some species are recorded as 

 pests of mushrooms. 



Fig. 540, Exechio nativo Johannsen. 



10a. Anal spiracles at the apices of a pair of long stalk-like proces- 

 ses. Fig. 541 Family SCATOPSIDAE 



The larvae live in dung, in 



Kig. 541. Rhegmoclema atrata Say. 



decaying organic matter, or un- 

 der the loose bark of decaying 

 trees. Their adults are known 

 as dung midges, or minute 

 black scavengers. 



192 



