12 



BULLETIN 807, U. S. DEPAETMEISTT OF AGRICULTUKE. 



Table IX. — Graphic chart of life history of Bruchus rufimanus for seasons 



of 1911-18 ana 1918-19. 



Jan. 



Feb. 



Mar. 



Apr. 



May. 



June. 



July. 



Aug. 



Sept. 



Oct. 



Nov. 



Dee. 





Eggs, 

 Larvas, 

 Pupae, 

 Adults, 



- 













































































































1 





























Contin 



uous line=l 



317-18. 



Broken 1 



ine=1918-19. 















Althougli a few adults may be found as late as June, the majority 

 die before the end of March. During 1917 a number of badly in- 

 fested beans were inclosed in a box. Ten per cent, of the weevils 

 were dead by February 1, 50 per cent by March, and 90 per cent by 

 the 1st of April. A very few remained alive until June. The re- 

 sults of field observations at Hayward during 1918 as to the preval- 

 ence of weevils in the fields are recorded in figure 5. Each count 

 represents an examination of horse-bean plants for a period of 15 

 minutes. 





/a 



Fig. 5. — Curve showing abundance of broad-bean weevils in a field at Hayward, Calif., 



1918. 



Adults have never been observed in the field before the latter part 

 of March, but it is evident that some of them must live through the 

 winter, hiding in the soil, or among rubbish, leaves, etc. In experi- 

 mental plantings of infested beans, both in the fields and in pots, 

 live adults have been observed to come out of the soil several days 

 after planting. In one case a germinating bean was dug up two 

 weeks after it had been planted, and a live weevil, which had emerged 

 from the bean, was found clinging to it. In another germination. 



