No. 555] SPECIES-FORMING OF ECTO-PARASITES 1 47 



that I was a temporary host for individuals of parasites 

 more normal to a duck or a barn owl than to man ! But 

 these wanderers seemed as anxious to leave their chance- 

 found new host as was the host to be relieved of them; a 

 few moments was the usual extent of their stay. 



This point of the reluctance of Mallophaga to migrate, 

 even with good opportunity, from normal or characteris- 

 tic host, to another, is emphasized when we come to ex- 

 amine the parasitic conditions of the next bird order, the 

 Accipitriformes, or falcons, hawks and eagles, almost all 

 species of which capture living mammals of one kind or 

 another. In the parasitic records of the seventy species 

 of this order included in my host list, there is not a single 

 record of a Mallophagan species of either of the strictly 

 mammal-infesting genera, and there are but three or four 

 records of bird-infesting species that are plainly strag- 

 glers from prey, as is, for example, a typical duck para- 

 site recorded from an American hawk, and a pigeon para- 

 site from a European falcon. In fact, the Mallophagan 

 species taken from the birds of prey are about as charac- 

 teristic of their host-group as are those of any other 

 group, although there are, indeed, no parasitic genera 

 wholly peculiar to the birds of prey. The Mallophagan 

 species Colpocephalum flavescens is found on twenty-one 

 Accipitrine species and Nirmus fuscus on eighteen, the 

 hosts representing species from all parts of the world, 

 including, for Nirmus fuscus, at least, Australia. They 

 represent, too, most of the principal families and sub- 

 families of the order. Colpocephalum flavescens is found 

 on Thrysa'etos, a new world eagle genus, on Gypaetus, an 

 old world eagle, and on one cosmopolitan species of A quila 

 and one old world A quila. The eagles, like the great vul- 

 tures, are characteristically solitary birds, only the mem- 

 bers of each household, that is, male, female and young, 

 coming into contact with each other. They are typical 

 host islands. Some of the birds of prey are strongly 

 Parasitized, as the golden eagle, Aquila chrysaetus, with 



