DIPTERA 855 



spines along the costa (Fig. 1109); the subcostal vein is distinct; the 

 oral vibrissas are present ; the postvertical bristles, which are located 

 on the back of the head somewhat behind the ocelli, are convergent; 

 and the tibiae are armed with spurs and with preapical bristles. 



The flies are found in shady and damp places; many of them have 

 been found in caves; and some species on windows. 



Fig. 1 109. — Wing of Leria. (After WilHston.) 



"The larvae of Leria have been bred from bat and rabbit dung; 

 those of Helomyza from truffles, decaying wood, etc." (WilHston) 



The family was monographed by Aldrich and Darlington ('08) ; 

 they recognized ten genera and about two score species found in the 

 United States. 



The family BORBORID^ is composed of rather small or very 

 small black, brown or obscurely yellowish flies, having a quick short 

 flight. Some of the species are very common, occurring in great num- 

 bers about excrement or near water. These "dung-flies" differ from 

 those of the Cordyluridas in that the subcostal vein of the wings is 

 wanting or indistinct and in having the hind metatarsi dilated and 

 usually shorter than the following segment. 



The larvce of some of the species, at least, live in excrement. 



The family PHYCODROMID.^ includes only a few species of 

 flies that are found among sea-weeds along the sea-shore. Two species 

 are listed from Alaska and one from California. This family is named 

 the Coelopidse by Hendel ('22). 



Family SCIOMYZID^ 



The members of this family are usually brown or brownish yellow 

 in color; and in many species the wings are spotted or infumated. 

 They are usually found in moist situations, as along the banks of 

 streams. The larvae are aquatic. 



These flies lack vibrissee. The face in profile forms a sharp often 

 very acute angle with that of the oral margin. The postvertical 

 bristles are divergent when present. 



This family is represented in this country by more than twenty 

 genera and by nearly one hundred described species. It has been 



