( cxlix ) 



parts living exclusively on bats is remarkable, and yet similar 

 instances of convergence are not rare among non-parasitic 

 insects, as for example the modification of the fore-tibia into 

 an instrument for digging, the hind-legs into organs for 

 jumping, etc. Such modifications are in fact adaptations 

 suited for a similar kind of life and acquired by the various 

 insects independently of one another. 



Some of the chief activities in the life of the Epizoa and 

 the attendant morphological peculiarities aim at the circum- 

 vention of the hostility of the hosts. Beak, tooth, and claw 

 are ever ready to destroy the unwelcome guests. As among 

 insects generally protective resemblance, nauseousness, stings, 

 shamming death, swiftness of flight, etc., are means of avoid- 

 ing an untimely death, so we find also among Epizoa devices 

 which give the parasite a chance of surviving the severest 

 persecution. These morphological devices may be discussed 

 under two headings : (1) Means of holding on to the host, 

 and (2) means of moving about on the host into a position 

 of safety. 



The Ectoparasite is enabled to keep his foothold, so to 

 speak, by bristles, tarsal claws, or the proboscis, or a com- 

 bination of them. 



It is one of the characteristics common to Epizoic in- 

 sects that they have a covering of hairs and bristles, either 

 over the whole body or on certain exposed portions of it. 

 The bristles and hairs serve various purposes. The function 

 of those bristles which are directed away from the body or 

 legs is to rest on the hairs of the host when the parasite is 

 not moving. The parasite by this means can hang in the 

 pelt without slipping out, as a broken-off many-branched 

 twig remains hanging in a bush. These supporting bristles 

 are directed backwards, or at least their tips point back- 

 wards, so as not to impede a forward movement of the para- 

 site. Some Epizoa can only move forward in the pelt (Siphon- 

 aptera), not backwards. Some Mallophaga resemble Poly- 

 ctenidae in possessing single long bristles on the tibiae (cf. 

 text-figs. 26-29). 



The claws at the end of the tarsi appear to be organs which 

 axe easily modified. The claws of the fore-tarsi are often 

 different from those of the other tarsi in Ectoparasites, as is 



