PARASITISM 



131 



season. Many of our caterpillars have a dense covering of long hair which, 

 we would suppose, might prove an effective protection by keeping the 

 mother-by at a istance as she seeks a host for her progeny. This is 

 not the case, however, for we find that the wooly-bears, the very hairest 

 of our caterpillars, are very frequently parasitized. The egg is attached 

 to the hair and the young parasite after hatching wriggles down to the 

 skin. It sometimes happens that the caterpillar is almost full grown 

 before it is parasitized. In this case the caterpillar may spin its cocoon 

 and even pupate before the parasite develops, but, as stated before, the 

 host never, except possibly in very rare cases, raches the adult stage. 

 The third group of fles parasitic on the larvae of other insects is 

 called Borabjliidae. They are flies which are short and robust, usually 

 with a thick covering of hair which gives them a downy appearance. 

 The wings of many are beautifully mottled with brown or black. They 

 are found most abundant about damp places in the woods, along the roads, 

 or on flowers, and are extremely active in flight, hovering motionless in 

 the air for a moment, then darting away so swiftly the eye cannot 

 follows. Some of the Bombyliidae are parasite in the larvae of moths 

 but the majority choose the larvae of our various wild bees for their 

 hosts. 



A Tachinid fly (Belvosa bifasciata). 

 [After Riley.] 



A Bmobylid fly {Anthrax hypomelas). 

 ]From Insect Life. ] 



