88 INSECTS AFFECTING STORED PRODUCTS. 
with eggs. The beetles were also removed. On July 12 two males 
emerged from this lot and the first bean opened disclosed a newly 
hatched beetle. Allowing at least a day for the beetle to mature 
sufficiently to gnaw through the outer shell of the bean, we have in 
this case the completed life cycle in 15 days. 
NUMBER OF GENERATIONS. 
It will be readily seen that with a species capable of developing in 
from three to eight weeks according to temperature, we have a possi- 
bility in a heated atmosphere of six, seven, or even eight generations 
annually. Knowing the effect of temperature on the development of 
insects in general, and of a rapidly breeding species like the present 
in particular, we may say approximately that throughout the coldest 
months in the District of Columbia, January and February, in stor- 
age in a heated temperature of about 70° F., it is possible for one 
generation to develop; in the higher temperatures indoors during 
March, April, and May, two generations; in the still higher tem- 
peratures of June, July, and August, one generation in each month; 
in September and October, one generation; and between the latter 
part of October and the last of December another generation, making 
a theoretically possible annual total of eight generations. There is apt 
to be a resting stage, however, at some point, as was observed on one 
occasion. During the second week of April, in a heavily infested lot 
of seeds where the beetles were emerging in large numbers, literally 
by hundreds almost every day, development suddenly ceased and the 
beetles did not again appear until about a week later. Two days 
afterwards they had again become abundant. In cool temperatures 
the number of generations will be less—three, four, or five—while in 
colder temperatures the species will probably not survive. 
Some other records, the details of which have not been preserved, 
are available showing that the egg period in the high temperature of 
midsummer weather may be four or five days and the pupal stage 
a similar period. A summary of the different periods is shown in 
the following table. The larval periods are necessarily estimated by 
subtracting the pericd of incubation and that of the pupa from the 
total life cycle. The other periods which are indicated in the table 
by a star (*) have been estimated in a similar manner; the remaining 
pericds have come under actual observation. 
Developmental periods and life cycle of the cowpea weevil, 
March-May. June-July. Minimum. | Maximum, 
© as ois 
1 of ee Oe ease OMe Boece Ieee ne ss &, 10 SER EATON 468 3*, 4 10 
Gish We Bae ma ae ot c auicia yc Con aban Oe Sea nd SOMBRE 17, 25, 40 |12, 13, 18 12, 13 40 
Pipa as3ih Ph RRS ee 7, 10 3*, 4,°5, 6* 3*, 4 10 
Cycle. VAPONST BS were 450 30-145, 760181! 215 N80 | beats 60 
