MANUAL OF NATURAL HISTORY. 261 



34. Family.— Spider - Flies (Hippoboscidse). An- 



tennse immersed in anterior angles of clypeus ; 

 head circular, closely united to thorax ; eyes 

 large ; mouth covered with a membranous 

 plate perforate at end, and with bristly nar- 

 row plates on sides, extended to form a kind 

 of rostrum ; body clothed with bristles^ 

 short, depressed, leathery ; wings often rudi- 

 mentary ; head prone, the neck lying on 

 prosternum. Parasitic ; reside on birds and 

 quadrupeds, running about the hairs and 

 feathers with great agility. 



35. Family. — Bat-Lice (Nycteribiidse). Head turned 



back and upside down over mesonotum ; an- 

 tennae very short, two-jointed ; mouth with 

 two large lateral setose valves, and a central 

 style, enclosing several setae ; thorax flat ; 

 wings and balancers none, replaced by two 

 comb-like organs ; legs very long ; claws 

 strong, hooked. Parasitic on the bodies of 

 bats. 



FLEAS. 



The insects forming this small Order, though de- 

 prived of wings, yet have a regular metamorphosis? 

 and in their general structure, and especially of that 

 of their mouth, closely approach the Order of Flies, 

 with which indeed they are sometimes associated. 

 They are remarkable for their extraordinary strength, 



