10 ILLINOIS BIOLOGICAL MONOGRAPHS [130 



my sincere appreciation for a keen interest in the work and for many helpful 

 suggestions. Professor Ward also placed at my disposal his library and 

 his collection. 



Other material was obtained for study from Harvard University, the 

 University of California and the University of Pennsylvania. Doctor 

 Minnie Watson Kamm kindly donated an infected host collected in the 

 vicinity of Urbana and containing valuable material of Paragordius varius. 



The early collections were made under the direction of Professor Frank 

 Smith, while the work at Douglas Lake, Michigan, was made possible thru 

 the kindness of the director of the station, Doctor H. A. Gleason, and was 

 carried on under the direction of Doctor W. W. Cort. 



Many helpful suggestions were obtained from Doctor T. B. Magath and 

 other workers in Professor Ward's laboratory. 



MATERIAL AND METHODS 



The two species studied are Gordius robustus Leidy 1851 and Paragor- 

 dius varius (Leidy 1851), 



Gordius robustus is well known in America; its range extends from the 

 Atlantic to the Pacific. It is by far the most abundant species in the 

 streams near Urbana, Illinois, and is occasionally picked up in collections 

 made for the zoological laboratory of the University of Illinois. Eight 

 males and one female were collected among dead grass at the water's 

 edge in a small stream on March 25, 1914. Then, for nearly a month, 

 diligent searches in similar localities were fruitless. On April 18 several 

 more specimens were found. 



It was noted at the time that both localities were at the edges of rapids. 

 This led to the investigation of other rapids with the result that hundreds 

 of specimens were collected. It was possible to walk along the bank of a 

 stream and descend at rapids with grassy borders and collect Gordius in 

 masses containing sometimes as many as 25 or 50 worms. Collections 

 were made at short intervals until the middle of June. More material was 

 collected in 1915 and 1916. 



The material in the collection of Professor Henry B. Ward at the Uni- 

 versity of Illinois was available for study as well as Leidy's specimens of 

 1879 and the material from the collections at Harvard University and the 

 University of California. 



Eggs were found thruout the month of May and the larvae hatched 

 the latter part of May and during June. 



Parasitic stages were obtained in large numbers in the fall of 1914 and 

 again in 1916. Earlier stages were obtained by infecting the hosts in the 

 laboratory. About 500 specimens in different stages of development were 

 obtained for the investigation. 



Paragordius varius is even more abundant than the previous species and 

 is the one most commonly collected in this country. 



