OF WASHINGTON*, VOL. XVIII, 1916 199 



From our records on the seasonal prevalence of Pollenia, con- 

 sidered in the light of our studies on the developmental stages, 

 we reached the tentative conclusion that there are four broods 

 or generations per annum in the latitude of Washington. Large 

 fly traps baited with banana were in operation throughout the 

 season and the contents were killed, sorted, and counted each 

 week. We found small numbers of Pollenia in these traps from 

 the 1st of April to the middle of May at which time they almost 

 completely disappeared. The wings were frayed and the yellow 

 hairs rubbed off and they had the appearance of old flies which 

 had overwintered. Then we found freshly emerged flies from 

 May 25th on, the number gradually increasing until the maxi- 

 mum was reached during the week ending June 22, followed by 

 a sudden drop. Then another gradual increase began, culmi- 

 nating in another maximum during the week ending July 27. 

 This was repeated and the curve shows another marked ri.-e 

 culminating in the week ending August 31. We expect to find 

 this year, as was found in 1915, another marked rise in October. 

 It seems probable that the adults of this late generation emerg- 

 ing during October and November overwinter in protected situ- 

 ations and deposit eggs during the following April. The fact 

 mentioned above, that infested worms were not found during 

 the autumn or early spring, indicates that this generation does 

 not deposit eggs in the fall. The possibility of pupae overwinter- 

 ing in the soil is yet to be investigated. 



More complete studies are now under way upon which we 

 hope to report in detail later. 



Arinal date of inililicnlion, \<>r<-inlin- >7, 1916. 



