292 ILLINOIS BIOLOGICAL MONOGRAPHS [292 



Proteocephalus exiguus 

 P. exiguus has been found only in the Great Lakes. Its hosts, 

 Coregonus (Argyrosomus) artedi, C. nigripinnis, and C. prognathus are 

 all found in certain of the Great Lakes. C. artedi is in all the Great 

 Lakes and neighboring waters, and north to the Arctic regions, exclu- 

 sive of Alaska. C. nigripinnis is found in the small lakes of Wisconsin 

 and Minnesota and in Lake Michigan. C. prognathus occurs probably 

 in all the Great Lakes in deep water. Thus in Lake Michigan, at least, 

 these species are all found. As to food habits but few data may be 

 found for C. prognathus and C. nigripinnis. C. artedi feeds on Ento- 

 mostraca, small molluscs and crustaceans, with larvae of insects and 

 other animal forms including bottom fauna and spawn of the common 

 white fish. It seems probable that the other species take many of these 

 same food elements. Under these conditions the finding of this species 

 in three closely related hosts is not remarkable but is to be expected. 



Proteocephalus filicollis 

 This species is known only from the lower reaches of the streams 

 flowing into the Baltic Sea, into the North Sea and the waters adjacent 

 thereto. It apparently does not occur in the Alpine lakes. Its hosts 

 are Gasterosteus aculeatus and G. pungitius. The latter is found all 

 over north Europe (not in south Germany) and in North America as 

 far southward as the Great Lakes region. G. aculeatus has a more 

 restricted distribution being confined to the fresh and brackish or saline 

 waters of Europe with the exception of the Danube drainage system. 

 Thus the two species occupy north Europe in common. In food habits 

 the species are much alike. Both are voracious plankton feeders; both 

 take also fish-eggs and fry, and bottom fauna. These are the conditions 

 which one would expect to find if the two species harbor the same para- 

 site species. Specimens of G. pungitius from North America should be 

 examined in order to learn whether they harbor the same species of 

 parasite as the European specimens. 



Proteocephalus longicollis 



This species has a wide distribution in Germany and is known also 

 from Switzerland. It is unknown in southern Europe, Russia or in 

 France. It has been reported from Hungary, probably as the result of 

 a misdetermination. Its reported hosts are mainly salmonids tho the 

 list includes one esocid, one percid, and three cyprinids. The accom- 

 panying table names the hosts and shows the distribution and food of 

 each. An examination of the table shows that in a general way these 



