DIPTERA 871 



or silvery, tessellated or changeable pollinose ; vein Mi +2 has an almost 

 angular bend and ends considerably before the apex of the wing; 

 the sides of the face are hairy ; and the arista of the antennas is plumose 

 above and below for nearly half its length or a little more. None of 

 the species has discal machrochgetae on the abdominal segments, 

 hairy eyes, long proboscis, rudimentary palpi, or more than a single 

 pair of discal scutellar bristles. 



So far as is known all species of this family are larviparous. The 

 different species show a wide range in larval habits; but by far the 

 greater number of the species that have been bred are parasitic in 

 other arthropods. They have been bred from various insects, from 

 scorpions, and from the egg-sacs of spiders. Several species have 

 been bred from dead fish ; and a considerable number from the excre- 

 ment of mammals. Five or six species live only in the tubular cups 

 of pitcher-plants (Sarracenia) , feeding on the dead insects found 

 there. It has been found that Sarcophaga hcBmorrhoiddlis is some- 

 times the source of intestinal myiasis in man, and several cases of 

 cutaneous myiasis caused by larvae of Wohlfdhrtia vigil have been 

 described by Walker ('22 a). 



For the determination of species of this family one should consult 

 the moEC9Taph by Aldrich ('16). 



Family TACHINID^ 



The Tachina-Flies 



The tachina-fiies are often found about flowers and rank vege- 

 tation. They are usually short, stout and bristly (Fig. 11 17). They 

 differ from the following family, the Mus- 

 cidae, in that with the tachina-flies both 

 the hypopleural and the pteropleural 

 bristles are present; and they differ from 

 the two preceding families, the Calliphor- 

 idae and the Sarcophagidas, in that in this 

 family the second ventral abdominal 

 sclerite, as well as the others, is more or 

 less covered, sometimes wholly, by the 

 edges of the dorsal sclerites. 



This is a very large family, more than ". ^ ^ u- a 



£ ^ 1 J J • 1- ^ J r Fig. 1 1 17. — A tachina-fly. 



fourteen hundred species are listed from f^arva, adult, puparium. 

 North America alone; and from the and eggs upon the fore 

 standpoint of the agriculturist it is the part of an army-worm, 

 most beneficial family of the Diptera. 



This family includes two subfamilies; the Dexiinae, and the 

 Tachininas, each of which is regarded as a separate family by some 

 v/riters. 



The larvse are parasitic, chiefly within caterpillars, but they have 

 been bred from members of several other orders of insects. An ex- 

 tended list of tachinid parasites and their hosts is given by Coquillett 



