EFFECTS OF TEMPEEATURE ON WHITE FLY. 29 



few adults remained in fliglit, while the first eggs deposited were 

 hatching. All eggs were hatched by October 5 and by October 20 

 many insects had reached the pupal stage. 



Investigations at Raj pur and Saharanpur revealed conditions com- 

 parable with those at Lahore. Observations throughout northern 

 India in November of the previous year (1910) showed the insect 

 at that time to be in the pupal state. From a consideration of these 

 conditions found in two different years it is evident that the white 

 fly passes the winter in northern India as a pupa. 



Number of Broods of the Citrus White Fly. 



It has been stated by Morrill ^nd Back that while there may be 

 in Florida from three to six generations, adult flies are found in 

 greatest abundance only during three more or less distinct periods, 

 or generally speaking, there are three broods of white flies each year. 

 Strictly spealdng, there is great irregularity of breeding and overlap- 

 ping of generations so that adult white flies may be found in varying 

 numbers at aU times except during the colder periods of Avinter. In 

 aU this irregularity, however, there stand out in prominence three 

 general broods — a spring, a summer, and an autumn one. 



Turning to northern India we find a different condition. Here 

 there were two very distinct broods on citrus trees m 1911, adults 

 of the first emerging in early April and those of the second during the 

 fu'st part of September. So far as the writer's observations extended 

 these broods were sharply defined and without overlapping genera- 

 tions. In fact, so sharply defined were these two broods that no 

 adult flies were seen outside of the two normal periods of emergence 

 with the exception of a very few during three to four days in June. 

 The latter emergence was due to a preceding period of *high humidity 

 accompanied by slight rains. 



The Effects of Temperature on White-fly Development. 



The climatic conditions of the plams of northern India are very 

 different from those of Florida, and the resultant eft'ect on the devel- 

 opment of tKe white fly is equally apparent. 



Whereas the winters in the Punjab of India average colder than in 

 Florida the summers are very much hotter. During the months of 

 July and August the average daily mean temperature in central 

 Florida is 82° F., while during the same period in 1911 at Lahore it 

 averaged 96° F., or 14° higher. The average daily mean tempera- 

 ture at Lahore for the months of May, June, July, and August was 

 94° F. and the average maximum temperature for the same period 

 was 107° F. Such high temperatures have naturally a deterrent 

 effect on insect development. Most of these days are bright and 

 sunshiny, and so penetrating is the direct action of the sun that 



