Dec. is, 1920 Rice Weevil, (Calandra) Sitophilus oryza 421 



about four eggs a day for a period of nearly 100 days. Taking 35 days 

 as the length of the average life cycle, we find that by the time the female 

 weevil has stopped laying eggs, or in about three months' time, the 

 progeny from a single pair of weevils would theoretically amount to 

 approximately 100,000 weevils. From this time on during warm weather 

 the increase would be extremely rapid and is left to the imagination of 

 the reader. 



LONGEVITY 



The length of life of the adult weevils is variable and depends upon 

 a number of different factors. With weevils that emerge during the 

 spring and summer months the average length of life is from three to six 

 months. In this case the weevils mate almost immediately after 

 emergence, and egg laying ensues. The female weevils continue deposit- 

 ing eggs until exhausted and then die. With weevils that emerge in the 

 fall and winter months, mating and oviposition are less frequent, the 

 weevils do not become exhausted so rapidly, and life is consequently 

 prolonged. Several female weevils that were kept segregated and were 

 not allowed to mate laid only a few eggs, did not become exhausted, and 

 were still alive eight months from the date of emergence. In another 

 case several weevils of both sexes were kept segregated for a period of 

 four months and were then allowed to mate. Of these, several weevils 

 of both sexes were still alive and active eight months from date of 

 emergence. 



Weevils deprived of food do not live long. In cold weather when they 

 are somewhat sluggish specimens have lived for 30 days without food. 

 In warm weather, however, they are very active and soon become ex- 

 hausted, seldom surviving for more than a week without food. 



FEIGNING DEATH 



When suddenly disturbed, the adult weevils often feign death, drawing 

 their legs up close to the body and dropping. This state does not last 

 long, and the weevils are soon hurrying off as active as ever. It is inter- 

 esting to note that the habit of feigning death is not nearly so well devel- 

 oped in this species as it is in the closely allied species Sitophilus granarius. 

 Weevils of the latter species feign death at the slightest disturbance and 

 remain motionless for a considerable length of time. The fact that S. 

 oryza possesses functional wings with which to escape, while S. granarius 

 does not, may have some bearing on the explanation. 



PARASITES 



Parasites of Sitophilus oryza are numerous and attack all stages of 

 this insect. A predaceous mite, Pediculoides ventricosus Newport, is 

 often found in weevil-infested corn in the southern States and attacks 

 and kills eggs, larvae, and pupse. 



Two hymenopterous parasites, Cercocephala elegans Westwood and 

 Aplastomorpha vandinei Tucker, are found in great abundance in Florida 

 attacking the larvae. 

 16917°— 20 2 



