542 SMITHSONIAN MISCELLANEOUS COLLECTIONS [vol. 50 



summer. The first larvae of this species were found, newly hatched, 

 at Oxbow, on May 6, in ditches along the railroad. The weather 

 continued cold for some time after this and the pools froze over at 

 night. This apparently did not injure the young larvae. On May 

 1 6 a large number of pools were examined, and it was found that 

 all but the larger pools contained larvae. The pool from which the 

 young larvae were obtained on May 6 now contained many larvae. 

 It was deep and large and the water cool ; in consequence the larvae 

 were still in the second stage. In smaller, shallow pools, where the 

 water was warm, the larvae were much further advanced. A shal- 

 low puddle in the field close by the railroad station, the water of 

 which was remarkably warm, contained numerous larvae, mostly in 

 the third stage. The larvae for the most part kept among the grass 

 close to the margin, where the water was warmest and they were 

 best protected from the wind. These larvae, brought into the house, 

 nearly all molted on the following day. A day later (May 18) a 

 number of the larvae pupated. In the meantime there had been 

 severe frosts during the nights and the pools were repeatedly frozen 

 over and thawed out again by the sun of the following day. But in 

 spite of this the larvae developed as rapidly out of doors as in the 

 house, the effect of the sun more than offsetting the retarding influ- 

 ence of the cold nights. The first adults were bred out on May 22. 

 Larvae continued to increase in numbers during the following week, 

 those in the small warm pools being most abundant and developing 

 most rapidly. The small permanent ponds contained no larvae. By 

 the end of the month the larvae of this species had practically all 

 disappeared. 



Adults of this species first appeared active on May 30 and a few 

 came to bite. They were first noted in numbers on June 5, a warm, 

 sunny day following four days of cold, cloudy weather. They came 

 drifting before the wind, and during calm intervals were very an- 

 noying. At 10.45 a - m -> on a r i se °f ground west of the town, the 

 highest rise on that part of the prairie, a swarm of about 50 males 

 gathered above my head. They emitted a high-keyed piping sound, 

 swinging backward and forward and swaying sidewise, all the time 

 facing the wind. With every gust of wind they were scattered 

 toward the ground, only to reassemble when the wind decreased. 

 When I passed the place again, at 12.45 P- m -> tne males were still 

 in evidence, although much interfered with by the wind. The same 

 day, at 5.30 p. m., another swarm of males was observed in the upper 

 part of a ravine, where the slopes were gentle. They were going 

 through rapid evolutions, darting forward and upward and drop- 



