FAMILY TACllIXID.K Till: TACl IIXIDS 417 



evidenced by their numbers. In at least one species the larvae resembling 

 little coiled cones, remain for long {)eriods on leaves, until they are 

 brushed by the hair of a caterpillar, when they suddenly become active, 

 make their way up the hair and enter the body. Most species, however, 

 apparently oviposit in or on the host and in the ease of manj' caterpil- 

 lars the egg shells remain attached to the larva for long periods, and 

 may be found on them as long as the larval skin exists. This is com- 

 monly the case Avith silk w^orm caterpillars parasitized by species of 

 Achaetoneura, but the characteristic is not restricted to this genus. The 

 literature on this subject is more extensive than one might imagine 

 although I must confess that I. am not familiar with it in its entirety. 



The study of the immature stages has been greatly stimulated be- 

 cause of the economic importance of these insects. A goodly number of 

 species have been imported to America in connection with the natural 

 control of foreign pests which have become established here and the 

 study of the grouj) has resulted. The best known of the imported 

 Tachinids is Compsilura cnncinnata Bouche, which is now well estab- 

 lished in the northeastern states and parts of eastern Canada, and is 

 spreading rapidly. Tliis species is one of the chief parasites of the Clypsy 

 ]\Ioth but it apparently attacks almost any kind of cateri^illar. Micro- 

 phthahna michiganensis Townsend, has been established in New Zealand 

 from shipments made ])y the Canadian government. Some of the species 

 imported have occurred in this country for many years and are perhaps 

 indigenous but it is not by any means certain that the native flies wall 

 attack the alien hosts. This point is mentioned merely to illustrate the 

 fact that the same species may have different habits in different regions. 

 It also demonstrates our lack of knowledge concerning these insects. 

 Parasites are searched for in all ])arts of the world, but most of those 

 we have introduced are from Europe and Asia. Just how many of these 

 introductions have resulted in the definite establishment of species in 

 this country w^e do not know, but there are some failures as well as 

 notable successes. Immediate results in control must not be expected, 

 but it seems likely that in due time a natural control of the pests will 

 occur. To expect the Tachinids, or other parasites, to control the pests 

 they are brought to fight within a few years is just as absurd as to have 

 expected the Pilgrim Fathers to have completely settled this country in 

 ten years. 



Tachinids occur everywhere and many s])ecies are common. Clear- 

 ings or lanes in woods are excellent for some species; most of them visit 

 flowers at some time or other, and many are found in grass. A few 

 species are nocturnal, others fly at dusk or on dark days and a number 



