EXTERNAL PARASITES OF BIRDS. 277 



must cause considerable harm. The problem, therefore, presents 

 a serious economic aspect. Henshaw ('08) states that this 

 parasite on bluebirds produces almost 100 per cent, mortality. 

 Plath in California found a mortality among nestling birds of 

 5 per cent, to 10 per cent. Coutant and Dufour report no 

 mortality among crows and swallows. The experiments of the 

 writer indicated no mortality, but young crows from parasitized 

 nests sho\\ed a marked retardation of growth, and young robins 

 became so weakened that a slight exposure to cold was suiiicient 

 to cause their death. However, in collecting, the parasitized 

 nests of bluebirds and house wrens were found t<> contain the 

 bones of nestlings. The presence of the jiai ins to 



indicate that they were responsible for the death-. \<> doubt in 

 the natural habitats the presence of these parasites weakens the 

 voting birds and indirectly causes their death by lowering their 

 -lance to unfavorable conditions and raii-ini; them t<> fall an 

 easy prey to other animals. 



Mallophaga, or bird-lice, are parasites which ha\- accompanied 

 the whole phyletic history of birds. Harrison ('14) who has 

 \\rittcn a very interesting paper on this subject says, "I uould 

 -u ^gest that the adoption of a parasitic habit by mallophagous 

 insects occurred even as far back as the late Mr--/i,ic tin In 



their primitive form he says they parasiti/ed both bird* and 

 marsupials before the true mammals differentiated out. H. E. 

 1 . \\ing identified some bird lice collected by the writer from 

 .1 . io\\ as Myrsuiea snbaqualis Lay. 



One does not usually think of fleas as parasite- on birds, but 

 they are to be found quite frequently in bird nests. Numerous 

 tlea* were collected from the nests of bluebirds, house wrens, 

 bank swallows, and house sparrows. Adult tK .<-. in copulation, 

 were taken from the nests of bluebirds, hon-e \\ien-, and house 

 spanou - \\hich \\ere collected in the month of January. A bank 

 -\\allo\\V nc.-t examined in June contained enormou- numbers of 

 larva-. Posted at the lower part of the hole which is the entrance 

 to the inhabited nests, are the adult fleas. They probably uti 

 themselves to the parent birds and are so spread throughout the 

 colony. All these fleas noted above were determined by R. C. 

 Shannon as belonging to the genus Ceratophyllus. 



