THE BIRD TICKS. 



(Family Hippoboscidce.) 



This group comprises a series of very remarkable flies which 

 are parasitic upon birds and mammals, moving quickly about 

 among the feathers and the hair. Unlike other external insect 

 parasites of vertebrate animals, many of them possess wings 

 although they are modified structurally in many other respects as 

 a result of their parasitic mode of life. One of the most remark- 

 able features of the bird ticks (as they are called), is the fact that 

 they not only do not lay eggs but that they do not lay larvae. 

 They are pupiparous insects, the eggs having hatched and the larva 



developed until the pupa 

 state is nearly reached 

 within the body of the 

 mother. They are ex- 

 truded by the parent fly 

 only when nearly ready to 

 become pupae. Bird ticks 

 are not very prolific; only 

 a single young is brought 

 forth at a birth. The pro- 

 boscis of the adult fly 

 differs from that of other 

 flies, and consists of two hard flaps which spread apart allowing 

 a tube to be thrust out from the head. 



Very little is known of the intimate life history of any of 

 them. Hippobosca equina is a winged species which occurs upon 

 the horse and which is known in England as the forest fly. 

 Possibly the best-known species is a wingless form known as 

 the sheep tick (Melophagus ovinus). In this insect the larva has 

 been shown to be nourished by secretions from certain glands of 

 the mother fly. One of the commonest of our North American 

 species is Olfersia americana v/hich is found upon several kinds 



188 



Fig. 109. — Olfersia americana. 

 (After Packard.) 



