PSYCHE. 



A PROBLEM IN DISTRIBUTION. 



BY VERNON L. KELLOGG, STANFORD UNIVERSITY, CALIFORNIA. 



In a systematic * paper on North 

 American Mallophaga, published in 

 1896,1 briefly outlined a "problem in 

 distribution" (pp. 48-57 of the paper 

 referred to) which seemed to me at that 

 time a very suggestive problem, indeed, 

 but which had a slightly uncertain note 

 in its assumption of certain foundation 

 facts. These assumed conditions had, 

 truly, all the seeming of facts, but there 

 failed a possible absolute verification of 

 them. A recent trip to Europe has 

 given me opportunity to examine (by 

 the kindness of Prof. Otto Taschenberg 

 of the University of Halle) a sufficient 

 number of type and authentically deter- 

 mined specimens of European Mallo- 

 phaga to supply the needed verification 

 of my earlier assumptions, and to dis- 

 cover further new and equally interest- 

 ing incidents of the problem. 



The problem, summarily stated, is 

 this: The species of the Mallophaga 

 (which are wingless, free-living, external 

 parasites on birds and mammals) are, 

 in a majority of cases, peculiar each to 

 some one host species. But the instan- 



* New Mallophaga I (Contributi 

 Hopkins Seaside Laboratory, (VI i 



i to Biology from the 



ces are many in which this condition of 

 distribution does not obtain, but where 

 a single parasite species is common to a 

 few\ or to even many, host species. 

 How does this latter condition come to 

 exist ? 



As the Mallophaga are wingless their . 

 power of migration from bird to bird is 

 evidently limited. They run strongly 

 and quickly, but they can live for only 

 a comparatively short time off the body 

 of the warm-blooded host, or on its cold 

 dead body. After a bird is shot the 

 Mallophaga on it die in from two hours 

 to three or four days ; in infrequent 

 instances I have found them alive on 

 the drying skin of the host at the end of 

 a week or ten days. Very rarely, indeed, 

 have I found Mallophaga under natural 

 conditions off of the body of the host. 

 Accounts have been given of finding 

 '• chicken lice " on the roosts in chicken 

 houses, a quite possible occurrence. 

 But even in such a likely place as an 

 ocean rock from which I had just 

 frightened hundreds of pelicans, como- 

 rants and gulls have I looked vainly for 

 Mallophaga which might be wandering 

 from host to host. 



