FIELD BOOK OF INSECTS. 



from the rushing water into the air above, where the 

 remainder of its life has to be passed? . . . During the 

 latter part of the pupal stage, which lasts about a fortnight 

 in all, the pupal skin becomes inflated with air, which is 

 extracted from the water, and passed apparently through 

 the spiracles of the fly into the space immediately within 

 the pupal skin. The pupal skin thus becomes distended 

 with air, and assumes a more rounded shape in consequence. 

 At length it splits along the back, in the way usual among 

 Insects, and there emerges a small bubble of air, which 

 rises quickly to the surface of the water and then bursts. 

 When the bubble bursts, out comes the fly." 



The larvae have, on their heads, brushes which gather up 

 food brought to them by the stream. This New Year's 

 I found them in large numbers where a much-used road 

 crossed a small brook; the automobilists apparently won- 

 dered what I was looking for in that cold water, but passed 

 on in ignorance of things far more interesting than so- 

 many miles an hour. 



BLEPHAROCERID^ 



The flat, aquatic larvae cling to stones in swift streams by 

 means of ventral suckers, one to each of the six sections 

 of the body, which are marked off by sharp constrictions. 

 The even flatter, heavily chitinized, shining black or brown 

 pupae are fastened by three pairs of pads. 



BRACHYCERA 



Having omitted several small families, we now reach 

 the flies with thick, few-segmented antennae. 



STRATIOMYID^E 



Some of the Soldier Flies are gay with yellow or green 

 and black cross-stripes on their flat, broad abdomens; the 

 abdomen is so wide in some species that it extends on each 

 side of the folded wings. The longitudinal veins are 

 crowded toward the front part of the wings, those which 

 are left in the hind part being much fainter. There are 

 numerous species, their larvae having various habits. 



246 



