HIBERNATION". 39 
Table XIII. — Length of prepupal and pupal stages, El Centra, Gal., 19J0. 
Exp. 
No. 
Date changed to prepupa. 
Date 
adult 
emerged. 
Length 
of 
period. 
Average 
mean 
temper- 
ature. 
Aug. 19. 
Aug. 22. 
Sept. 6.. 
Sept. 4.. 
Sept. 7.. 
Sept. 27. 
Aug. 21 
Aug. 24 
Sept. 8 
Sept. 8 
Sept. 9 
Sept. 29 
Days. 
2J-3 
2 
2-2| 
3 
2 
2J 
°F. 
C 1 ) 
( x ) 
2 84.9 
2 85.1 
2 87.0 
( ] ) 
1 Records missing. 
2 Temperature at Brawley, U. S. Weather Bureau. 
In the Imperial Valley the egg stage is from 4J to 5 days, the 
larval stage from 4 to 5 days, and the prepupal and pupal stages 
from 2 to 3 days, making the total life cycle only 10 to 12J days 
during the extreme summer temperature. 
The eggs were deposited within 2 days from the time the adult 
females emerged, so that a new generation might occur every 14 
days in midsummer. If the insect emerges from hibernation in the 
Imperial Valley at the same time as in Compton, there will un- 
doubtedly be 1 generation in the early spring occupying 30 to 40 
days, and then 2 generations a month for 5 or 6 months and 1 
longer generation in the fall, or 12 to 14 generations a year. Indeed, 
with such rapid multiplication it is not strange that crops in the 
late fall become seriously infested. 
SEASONAL HISTORY AT TEMPE, ARIZ. 
Mr. Wildermuth during October and November, 1911, made some 
observations on the life cycle of this thrips at Tempe. These gave 
a life cycle of very nearly the same duration as in the Imperial Valley 
in the warm weather, but in November the cycle was lengthened 
considerably. He found that specimens collected as larvse on October 
30 did not emerge as adults until December 1. This shows the same 
effect of cooler weather on this insect that the writer observed at 
Compton, Cal. 
Taking the results of Mr. Wilclermuth's and the writer's observa- 
tions on the bean thrips, there is a minimum life cycle of 10 days 
where the average mean temperature is about 88.75° F., and a maxi- 
mum of about 73 days with an average mean temperature of about 
53.58° F. 
HIBERNATION. 
This insect hibernates as an adult only, through most of its dis- 
tribution at least. It may be that in the more southern portions of 
its range it breeds continuously throughout the year, but our obser- 
vations in these localities mentioned have failed to show it. 
