Liitomology of the Illinois River. 257 



The place and maimer of oviposition have ah-eady been 

 described. Females were first seen ovipositing June 1, 

 though tliey had doubtless begun to do so some time 

 before, judging from the period of emergence. From 

 this time on they were constantly seen ovipositing in 

 ken to the cabin-boat produced young in ten days. The 

 favorable weather until late in July. Freshly-laid eggs ta- 

 very young larvae became conspicuously abundant early 

 in July, being especially- noted on the 10th at Station 

 G. The older larvae were common from early in May 

 till late in September, and a few were seen during the 

 winter in open water, although they seem to hibernate 

 mostly among drifted*material left by the waves upon the 

 shore. Collections made December 18 and February 26, 

 and also in March and April, show that a large part 

 of those which pass the winter are quite young. No- 

 vember 11 they were especially common on the shore 

 at Station G. 



Pupae were also often seen in the water, but occurred 

 in the largest number in April and May in the line of 

 drift left by the water at the highest point reached by 

 it earlier in the spring, some of the specimens being still 

 in the larval state. They were then some distance from 

 the water, and often quite dry externally. One was 

 found July 18, still alive, fully 100 feet back on a sloping 

 shore. May 17, on examining some fine drift where 

 the pupae were especially numerous, 1 noted a few 

 empty skins, and found two imagos just emerged. May 

 19, imagos were seen on herbage on the west shore of 

 Station C. They began to emerge during my absence, 

 between May 21 and 26, from pupae collected May 17, 

 and the last from this lot of pupae appeared June 27. 

 July 6 parasitic chalcids were seen in the cage, and 

 ekins of this species from which the paiasites had 

 emerged— as already- mentioned. The imagos collected 

 on the shores were all taken in May, males and females 

 in about equal numbers. They have also been collected 

 -17 



