10 



BULLETIN 807, IT. S. DEPAETMENT OF AGEICULTUKE. 



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 &. 



Mortality among the larvae after entering the beans is rather high. 

 This is so both in the case where by far more larvse 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 larvae of Bruchus rufimarms entering 

 beans toith the number reaching maturity. 



Number of beans. 



Number 

 of larvae 

 entering 

 beans. 



Number 



of 

 adults. 



Maxi- 

 mum 

 number 

 of larvae 

 entering 

 a bean. 



Average 

 number 

 of larvae 

 entering 

 a bean. 



Average 

 number 

 reaching 

 maturity. 



Percent- 

 age of 

 larvEe 



entering 

 beans 



reaching 



maturity. 



Percent- 

 age of 

 beans 

 entered 

 by larva. 



Percent- 

 age of 

 beans 



infested 

 with 



adults. 



100 



263 

 199 



226 

 72 

 64 



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 

 j)lanted. The duration of the adult stage varies considerably, de- 



