August iSgS.] 



PSYCHE. 



245 



But the commonness of a parasite 

 species to several liost species occurs 

 in cases where it seems impossible to 

 assume an actual migration. The hawks 

 have two or three parasites, as Docopho- 

 riis p/atystomiis, which are common to 

 several of them ; Docophorns cursor is 

 common to several owl species, Doco- 

 phorns excisus to several swallows, Doco- 

 phorns californiensis to several wood- 

 peckers, and Docophorns comviunis (with 

 its so-called varieties) to a great many- 

 passerine birds. The other genera of 

 Mallophaga present many similar cases. 

 Now in all of the cases mentioned, and 

 it is true of practically all of them 

 unmentioned, it will be noted that the 

 common hosts are closely allied forms, 

 /. <"., different species of a single genus, 

 or, and not infrequently, different but 

 allied genera. Only in the case of 

 Docophorns commnnis do we have a para- 

 site's range extending over family limits, 

 the hosts of this form representing sev- 

 eral passerine families. 



While actual migration in the just- 

 mentioned cases is almost an impossible 

 condition, there are other cases to which 

 I shall now refer in which the possi- 

 bility of actual migration is positively 

 precluded. These cases are those in 

 which a parasite species is common to 

 both American and European hosts 

 of different species and of habits and 

 geographical range which absolutely 

 preclude the possibility of the migration 

 of the parasites from one host species 

 to the other. A few details as to these 

 cases should be of interest. Two hun- 



dred and si.\ty-two * species of Mallo- 

 phaga have been taken from birds of 

 North America. Of these 262 species, 

 157 are new species while the remain- 

 ing 105 species are assumed to be 

 specifically identical with Mallophaga 

 originally described from European (or 

 Asiatic) birds. In a dozen or more 

 cases the American forms are called 

 varieties of the foreign species. The 

 determinations of the American speci- 

 mens, referred to European species, 

 were based on the descriptions and 

 figures of the European authors Nitzsch, 

 Giebel, Denny, Piaget, Taschenberg, et 

 al. In the case of Piaget and Taschen- 

 berg, especially, these descriptions are 

 detailed and excellent, and the figures 

 good. There existed, however, a doubt 

 in these determinations. As already 

 mentioned, I have recently had oppor- 

 tunity to e.xamine many European speci- 

 mens in the collections of the University 

 of Halle, and to compare with them 

 American specimens taken with me for 

 the purpose of this study. This com- 

 parison leaves no question as to the 

 specific identity of American and Euro- 

 pean specimens t.iken from different 

 host species. I could not make this 

 comparison for all of the 105 species 

 presumably identical, but could do it for 



* The records of the occurrence of these species dre 

 included in Professor Osboni's papers, notably his " Insects 

 Affecting Domestic Animals," Bull. no. 5, n.s., Div. of 

 Ent., U. S. Dep't. Agric. 1896, and in my New Mallo- 

 phaga, I. (iSg6), New Mallophaga, II, (i8g6), and New 

 Mallophaga, III, (now printing). Pi. very few records are 

 included in the works of European authors. The number 

 given, 262, is subject to correction, due to a 

 of duplication in Professor Osborn's and my paper: 



