1907.] 



Grain Weevils. 



413 



wing-covers are striated and also show punctures. C. oryzce 

 is very similar to C, granaria, but they may be distinguished 

 as follows : — 



Calandra granaria. 



All one colour, and with a more shiny 

 surface. Punctures on thorax larger, not 

 so close together, and oblong. No 

 functional flying wings. 



Calandra oryzce. 



The wing-covers have two orange- 

 coloured patches at the apex and at the 

 base. Punctures on thorax smaller, closer, 

 and rounder. Well marked flying wings. 



Larva. — The grubs are white, with yellow-brown horny 

 heads and biting jaws ; the body is wrinkled and without legs. 



Life History and Habits. — The females lay one egg in each 

 grain. The grub on hatching feeds on the contents of 

 the grain and when full fed pupates in the eaten-out 

 grain. In conditions extremely favourable to the weevils 



■ 5 



~ r J 



WEEVILS OF C. granaria (ON THE LEFT) AND C. oryicV (ON THE RIGHT), 

 WITH GRUB,' PUPA AND DAMAGED GRAIN. 



the whole life-cycle can be completed in a month, but 

 at lower temperatures and with the ordinary conditions a con- 

 siderably longer time is taken. Professor F. J. Cole* in his 

 experiments found that a temperature of 8o° Fahr. was the 

 most favourable for the development of the beetles. C. granaria 

 can stand out against lower temperatures than C. oryzce, 

 while the latter can, on the other hand, endure higher 

 temperatures than C. granaria. Moisture in the form of 

 water-vapour is very favourable for the weevils. Professor 

 Cole shows how a close and confined atmosphere favours the 

 weevils because it involves a rise in temperature and the 

 accumulation of water vapour. 



I have found that in small corked tubes containing grain 

 at ordinary temperatures, with the confined atmosphere and the 



'The Bionomics of Grain Weevils.'"— -Journal of Biology, 1906, Vol. I, Part 2. 



