38 O. E. PLATH. 



Prince Edward Island, in New Brunswick, Nova Scotia, Quebec, 

 Manitoba, and Saskatchewan. In this case it is difficult to make 

 any prediction. B. affinis occurs in New England, Ontario, and 

 Minnesota, and hence may yet be found in the adjoining eastern 

 and central portions of Canada. This seems all the more probable 

 when we consider that comparatively little collecting has been done 

 in these parts of Canada, and that the number of B re inns species 

 known from Illinois has been raised from 10 to 15 during the last 

 few years by the intensive collecting of Frison ('19). 



In the case of Ps. laboriosits and its host, B. vagans, we have to 

 assume either that Ps. laboriosus has more than one host or that 

 B. z'ogans is also present in South Carolina and Georgia and on 

 Prince Edward Island. B. vagans occurs in Nova Scotia, North 

 Carolina, and Tennessee, and it is therefore probable that it will 

 be reported from the adjoining territories mentioned above. 



In the case of Ps. variabilis and its host, B. pennsylvanicus, the 

 geographical distribution of the former only covers a small portion 

 of that of the latter, and it would. therefore not be surprising if 

 Ps. variabilis is taken in states from which it has not been reported. 

 In fact, its known geographical distribution makes it almost certain 

 that it occurs in Georgia, Indiana, and South Dakota. 



There still remain several other interesting questions in regard 

 to the members of the genus Psithynts, such as origin, similarity in 

 coloration with their hosts, and the frequency with which they 

 breed in Brcm-us nests. The most extensive records which we 

 have as regards the last of these three questions are those for one 

 of the European species, Ps. campestris. Hoffer ('88, p. 132) 

 records that he found more than 70 nests of B. variabilis and B. 

 agromm victimized by this species. Out of 48 nests of B. vari- 

 abilis, 13 contained Ps. campestris, and during several summers in 

 the early 8o's about half of the nests of these two Brcm-us species 

 harbored this parasite. In 1910 Frison ('16) opened seven sur- 

 face nests of B. pennsylvanicus, four of which were infested by 

 Ps. variabilis. Of the four B. vagans nests of which we have 

 records (one each taken by Putnam, Beutenmueller, Franklin, and 

 the writer), only one was later victimized by Ps. laboriosus, and of 

 two B. affinis nests examined (one by Franklin and one by the 

 writer), one was infested by Ps. ashtoni, while Ps. insularis was 



