42 Trans. Acad. Sci. of St. Louis. 



of the Falconidae. Thus Pterolichus nisi (Can.) is found 

 on six host species, but all of them belong to the Falconi- 

 dae and are closely related. 



If these forms are able to adapt themselves to lives 

 upon rather widely separated hosts, why have they not 

 done so as have many of the other forms? Since the 

 hosts are preying birds there would be a good chance 

 for them to get the mite parasites from the species 

 preyed upon, but such does not seem to have happened. 



Since the members of the Falconidae are non-grega- 

 rious and solitary in habits, thus making the transfer of 

 the parasites from one host to another improbable, it is 

 interesting to see how they became distributed among 

 several hosts belonging to this family. Doubtless it is 

 to be explained in the same manner as Kellogg has ex- 

 plained the host distribution of similar cases in the Mal- 

 lophaga, "that the parasitic species have persisted un- 

 changed from the common ancestor of the two or more 

 now distinct but closely allied bird-species.'* 



A List op the Sarcoptidae Known to Occur upon More 

 THAN One Host Species, Together with Their 

 Hosts. 



notoedres Raill. 

 N. notoedres (M6gn.) — Mus rattus L., M. decumanus Pall., Paludicola 

 amphibius (L.). 



pRosopoDECTEs Can. 

 p. chiropteralis (Trt.) — ^Rhinolophus ferrumequlnum (Schreb.), Vespe- 



rugo serotinus (Schreb.). 



SARCOPTES Latr. 

 3. caprae Fflrstb. — Capra hlrcus, Ovis aries, Equus caballus, Bos tauruB, 



Homo. 

 S. dromedarii r:«»rv. — Camelus dromedarlus L., C. bactrianus L., Lama 

 glaraa (L.), Giraffa camelopardalis (L.), Anti- 

 lope bubalis (sp.?). 



CNEMiDocoPTEs Ftirstb. 



€. mutans (Robin) — Gallus domesticus and other birds. 



