10 
BULLETIN 807, U. S. DEPARTMENT OF AGRICULTURE. 
point where the young larva entered, sometimes called the " sting," 
plainly shows on the dry bean as a dark spot varying in size from 
a pinpoint to almost as large as a pinhead. This is illustrated in 
Plate I, figure 2, a and h. 
Mortality among the larva? after entering the beans is rather high. 
This is so both in the case where by far more larvae enter a bean than 
could develop in it, and in the case where only one or two larvae 
enter, although the percentage of mortality is less with the latter than 
with the former. Table VI graphically illustrates this point : 
Table VI. — Comparison of the number of larrw of Bruchus ruftmanus entering 
beans with the number reaching maturity. 
Number of beans. 
Number 
of larvse 
entering 
beans. 
Number 
of 
adults. 
Maxi- 
mum 
number 
of larvas 
entering 
a bean. 
Average 
number 
of larvse 
entering 
a bean. 
Average 
number 
reaching 
maturity. 
Percent- 
age of 
larvae 
entering 
beans 
reaching 
maturity. 
Percent- 
age of 
beans 
entered 
by larva. 
Percent- 
age of 
beans 
infested 
with 
adults. 
100 
263 
199 
226 
72 
54 
132 
95 
86 
16 
29 
10 
7 
16 
9 
5 
2.63 
1.99 
2.26 
.72 
.54 
1.32 
.95 
.86 
.16 
.29 
50.1 
47.7 
38 
22.2 
53.6 
85 
78 
80 
40 
39 
70 
100 
63 
100 
58 
100 
15 
100 
26 
Average 
162.4 
71.6 
9.4 1.62 
.71 
42.3 
64.4 
46.4 
It will be seen from the table that although as many as 16 larvae 
may enter a single bean, the average number is about 2, and a total 
average of a little over 40 per cent reach maturity. Comparison 
with Table IV shows that while a maximum of from 5 to 16 larvae 
may enter a bean, the percentage of beans containing more than 2 
adults is small. 
The larval stage is from 10 to 15 weeks, the average being about 
12 weeks. 
Immediately after eating out the round hole in the cotyledon, 
already referred to, the full-grown larva becomes quiet, and in a 
short time pupates. At first the pupa is the same color as the larva, 
but gradually turns darker until it is a dark brown. 
The pupal stage is from 7 to 16 days with an average of 10 days. 
When the adult is first formed it is light brown and very soft, 
but it gradually turns darker and becomes harder. The adult may 
soon eat its way out of the bean through the " window " prepared 
by the larva, or it may remain in the bean for several months. In 
fact many adults never emerge from the beans at all, but die in them. 
If the weather is warm, or the beans are handled much, the weevils 
are apt to emerge from the beans sooner and in greater numbers 
than if the weather is cool and the beans are not handled much. 
Many of the adults emerge from the beans after the latter have been 
planted. The duration of the adult stage varies considerably, de- 
