THE TACHINA FLIES 



(Family Tachinidce.) 



This is a large and important group of flies, the members of 

 which have no common name except that of "tachina flies," by 

 which they are generally known to everyone who has studied 

 insects, even if his studies have not carried him into the order 

 Diptera, for all or nearly all of these creatures are parasitic upon 

 other insects and a person engaged in rearing caterpillars will 

 often have his ultimate design frustrated through the work of the 

 larvae of these flies. As a rule they are medium sized or rather 

 large flies of a gray tint, rather unattractive in appearance and 

 perhaps resembling the common house-fly as a rule. In fact, one 

 may say that they belong to the house-fly type. The gray body 



color is frequently striped with dark 

 or lighter stripes and there are some 

 marked exceptions to this general 

 colorational scheme as, for example, 

 in the dark-winged, sometimes red- 

 dish-bodied Trichopodas, the slender 

 Xanthomelaenas and Hemydas,the red- 

 bodied Echinomyias and those species 

 of the genus Archyias which look like 

 blue-bottle flies. In general the wings 

 are clear, the bodies are somewhat 

 bristly and the insects fly with a buzzing sound which is not 

 very pronounced but like that of a house-fly. They are active 

 and fly usually in the sunshine, being much less in evidence on 

 cloudy days. 



In their relations with man the tachina flies are beneficial — 

 the most beneficial group of Diptera, with the possible exception 

 of the syrphus flies. With the tachina flies, however, the habits 

 are much more uniform and the larvae feed only upon living 

 insects. By far the favorite hosts of these flies are the leaf-eating 

 caterpillars and the numbers which are destroyed in a single 



158 



Fig. 87. — Winthemia quadri- 



pustulata. 



(After Comstock.) 



