THE BROAD-BEAN" WEEVIL. 



Table V 



-Number of eggs of Bruchun rnjimunHH (IcjHJsitcd mi pods at Ilay- 

 ward, Calif. 



Date. 



Number 

 pods on 

 plant. 



Total 

 niiinl)er 

 eggs por 



plant. 



Number eggs per pod. 



Maximum. 



Minimum. 



Average. 



1910. 

 April 20 



12 

 19 

 5 

 12 

 14 

 8 

 8 

 11 

 10 



88 

 153 

 30 

 70 

 119 

 71 

 48 

 115 

 144 



17 

 17 

 18 

 29 

 22 

 19 

 9 

 23 

 42 



2 

 1 

 2 

 1 

 1 

 4 

 3 

 2 

 8 



7.3 



Do 



8 



April 25 



6 



Do 



5.8 



Do 



8.5 



Do 



8.8 



Do 



6 



Do 



11.3 



Do 



14 







No eggs were obserA'ed by the writer except on the pods, the hitter 

 varying in size from less than an inch to full growth of 5 inches. 

 Most of the eggs are found on the larger pods. 



Although adults have been noticed a number of times crawling over 

 the plants during the day, the act of oviposition was never observed. 

 It is probable that it occurs late in the evening or at night. 



Efforts to induce oviposition in captivity were not successful, so the 

 total number of eggs laid by individual females was not ascertained. 



The duration of the egg stage was found to be from 9 to 18 days, 

 with an average of 13 days. A few clays before hatching the dark 

 head of the embryonic larva can be seen plainly through the egg- 

 shell. The larva draws its head back, leaving about one-quarter of 

 the shell hollow. For about a day the position appears to be un- 

 changed, then graduallj'^ as the larva eats through the side of the 

 shell attached to the pod and into the pod the clear space in the 

 shell becomes larger until the latter is entirely empty, having a 

 glass}^ and transparent appearance. It usually takes about two days 

 from the time the larva begins eating through the shell until it is 

 entirely out of the latter and into the bean pod. 



The young larva begins feeding when the bean is green, and it is 

 well along toward maturity before the bean dries up. The amount of 

 food consumed is small compared with what other insects eat. It ap- 

 pears that the young larva often eats out a short tunnel, advancing a 

 little distance from the point where it entered the bean. When the 

 larva gets larger it eats out a hole somewhat its own shape, and about 

 50 per cent larger, as is shown in Plate I, figure 3, a and h. 



"When the larva reaches maturity, and just before pupating, it eats 

 out a round hole in the cotyledon, directly under the epidermis. The 

 hole is plainl}' seen through the half -transparent skin or " window," 

 which is broken easily by the adult weevil when it is ready to emerge 

 (see upper beans in PL I, fig. 5). The hole is seldom at the spot 

 where the larva entered, but at varying distances from it. The 



132902°— 19— Bull. SOT 2 



