DIPTERA 



821 



The larvae vary in habits ; some species feed on decaying matter, 

 while others attack the roots of growing plants, especially of grass. 



M,+, 



Fig. I 04 I. 



Wing of Bibio. 



Afi+1 



They have ten pairs of spiracles, which is a rather large number, al- 

 though there are other insects with as many. The pupae are usually 

 free. 



For descriptions of our species of bibionid flies see McAfee ('21). 



Family SCATOPSID^ 



This family includes minute black flies ; our known species measure 

 in length from less than one millimeter to three millimeters. Formerly 

 these flies were included in the Bibionidae; but they differ markedly 

 in the venation of their wings from members of that family. In the 

 Scatopsidas vein Cu forks 

 at or very near the base /?, 



of the wing (Fig. 1042) 

 and the cross-vein m-cu 

 is wanting. In some 

 species there is a vestige 

 of an anal vein but 

 usually there is none. 



This is a small family, 

 only about a score of 

 species are known from 

 our fauna; these are de- 

 scribed by MelanderC 1 6) . 



Most of the known larvae live in excrement. One species, Cobol- 

 diaformicdrimn, is believed to be myrmecophilous, for the adult was 

 taken as it crawled from a populous nest of the carpenter ant. In 

 this species the wings are vestigial. 



F.\MiLY SIMULIIDAE 

 The Black-Flies 



The common name, black-flies given to the members of this family 

 is not distinctive, for there are many species of other families that are 

 of this color; but like many other names that are descriptive in form, 



Fig. 1042. — Winj 

 Melander.) 



of Reichertella collaris. (After 



