SURROUNDINGS OF GROWING INSECTS 221 



dipterous parasites. 1 Many of these can feed indifferently 

 on a number of hosts. 



The Diptera, whose larvae live in this manner, are mostly 

 members of the family Tachinidae, allied closely to the blue- 

 bottle family (Muscidae), but with the adults distinguished 

 by the absence of fine hairs (" feathering ") on the terminal 

 " bristle " of the feeler. Most tachinid flies Tachina larvarmn 

 (Fig. no), for example deposit their eggs on the body of the 

 host-caterpillar, into which the maggots, when hatched, bore 



FIG. IIO. 



a, Tachina larvarum, a Parasitic Muscoid (female), x 5. 6, head of 

 Tachina (side view) showing eye, proboscis, and feeler with unfeathered 

 bristle, x 10. From Howard and Fiske, U.S. Dept. Agric. Ent. Bull, 91. 



their way by means of their sharp mouth-hooks ; the maggot 

 of Tachina devours the moth-caterpillar internally, and 

 generally kills it before the pupa has been formed. 

 Compsilura concinnata, another tachinid, is ' viviparous ", 

 the eggs hatching within the vagina of the mother, whose 

 sharp " larvipositor ", situated beneath the abdomen, pierces 

 the caterpillar's skin and thus places the tiny maggot safely 

 inside the host's body ; the maggots make their way to the 

 wall of the food-canal in which they feed. Most remarkable 

 is the habit of Blepharipa scutdlata, whose eggs are laid 



1 L. O. Howard and W. F. Fiske : " The Importation into the United 

 States of the Parasites of the Gipsy Moth and the Brown-tail Moth ". U.S. 

 Dept. Agri. Entom. Bull. No. 91. 1912. 



