262 



THE AMERICAN NATURALIST [Vol. XLVI1I 



sites without accepting new ones from its many, various 

 and closely pressing neighbors. 



Of the four Mallophagan genera found on the kanga- 

 roo, three, namely, Boopia, Latumcephalum and Hetero- 

 doxus 1 are peculiar to them. The third genus, Tricho- 

 dectes, is represented by but a single species which has 

 been recorded but once. This is the common Mallophagan 

 genus of mammals generally. The record is perhaps a 

 good one, but its lack of confirmation by being unrepeated 

 either Xor the same species or for any other species of 

 Trichodectes, is suggestive. Heterodoxus, Latumcepha- 

 lum and Boopia are two-clawed genera ; that is, they are 

 M;ill(>|iii;m;in forms which helong to a family all the other 

 genera of which are confined to birds. The characteristic 

 structural difference between the mammal-infesting 

 Mallophaga and the bird-infesting species is the presence 

 in the first group of a single claw on each tarsus, and in 

 the second of two claws. This difference is plainly an 

 adaptive one concerned with the fitting of the foot for 

 the seizing of hairs and scrambling about among them, 

 on the one hand, and the manipulation of feathers and 

 moving about on them, on the other. In examining living 

 specimens under the microscope the special use and fit- 

 ness of the feet, in the one case adapted to hairs and in 

 the other to feathers, is obvious. However, Heterodoxus, 

 Latumcephalum and Boopia, and, in addition, perhaps 

 one other doubtful genus, represented by one species, and 

 perhaps two or three species of another two-clawed 

 genus, constitute exceptions to the general rule. It is of 

 decided interest to note that the only genera of two- 

 clawed Mallophaga found exclusively on mammals are 

 limited to the Marsupials. The antiquity and isolation of 



i The single valid species of this genus— the two or three that have been 

 named are undoubtedly all the same — has also been recorded from dogs! In 

 fact specimens in my own collection were received with the record "from 

 Japanese dog. ' ' And Enderlein has recorded it from a dog from China and 

 Neumann from a dog from Formosa. Yet dogs ordinarily do not harbor 



liev e P that the dog hos^records indicate cases of straggling from kangaroos 



