136 journal of economic entomology [vol. 9 



Afternoon Session 

 Wednesday, December 29, 1915, 1.30 j). m. 



President Glenn W. Herrick: We will have the first paper this 

 afternoon by !Mr. Schoene. 



NOTES ON THE BIOLOGY OF PEGOMYA BRASSICiE BOUCHER 



By W. J. ScHOEXE, Blacksburg, Va. 



This paper deals with some conditions that affect the number of 

 broods. The spring brood of adults or those emerging from the over- 

 wintering pupse, are comparatively regular in their time of appearance. 

 This fact has been vouched for by many entomologists. The time 

 that the first flies emerge in the spring depends somewhat upon the 

 w^eather. During six seasons the first inchviduals were taken about 

 the time the Windsor cherries were in bloom, nr between the 1st and 

 16th of May. By covering small areas of infested cabbage fields 

 with cloth screens, and catching the flies as they came from the soil, 

 it was learned that the adults emerge during a period of five weeks or 

 longer. Our results also suggest that the time the flies first appear 

 in spring may be influenced by such characters as type of soil, depth 

 to w^hich the field has been plowed, and the slope of the land. 



The adults maturing in mid-summer are very irregular in their time 

 of appearance. There are probably several factors that contribute 

 to this irregularity, but it is primarily because the younger stages of 

 the insect are affected by the weather, and that the pupal stage may 

 be greatly prolonged. This irregularity in the life-history of the insect 

 was noted by Shngerland, who states as follows: " Most of the puparia 

 under our observation gave out the flies in about twenty days, in 

 June; with some it lasted only fifteen days, with quite a number, 

 nearly two months, with others three months " Shnger- 

 land also observed that, "these are very surprising facts W'hen one 

 understands that all of these puparia came from the first brood of 

 maggots. There is no hint in literature to any such retardation in 

 development." We have noticed this delay of development as de- 

 scribed many times. At first it was believed to be due to unnatural 

 conditions maintained in the breeding cage. However, by placing 

 the insects outside, and by screening portions of fields containing 

 infested plants, we learned that the retardation behavior mentioned 

 by Shngerland occurs regularly, each summer, in western New York. 



^Contribution from the Department of Entomology of the New York State Experi- 

 ment Station, Geneva, N. Y. 



