﻿28 BULLETIN 1393, U. S. DEPARTMENT OF AGEICULTUEE 



LENGTH OF DEVELOPMENTAL PERIOD 



The length of the developmental period of the granary weevil is 

 comparatively short dm-ing moderately warm weather. The cycle 

 from egg to adult is recorded in Table 7. 



Table 



7. — Duration 



of the 



developmental period of the granary 



weevil 







Number of days in — 



Num- 

 ber of 

 days 

 from 

 egg to 

 adult 



Mean 

 temper- 

 ature 

 for 



No. 



Number of days in— 



Num- 

 ber of 

 days 

 from 

 egg to 

 adult 



Mean 



No. 



Egg 



Larval 



Pupal 



Egg 



Larval 



Pupal 



ature 

 for 





stage 



stage 



stage 



period 





stage 



stage 



stage 



period 













p 













o p 



1 



5 



20 



5 



30 



80.4 



23 



4 



24 



6 



34 



80.0 



2 



4 



27 



5 



36 



80.4 



24 



5 



32 



6 



43 



77.3 



3 



4 

 4 

 4 



21 

 25 

 22 



5 

 5 



7 



30 

 34 

 33 



80.4 

 80.4 

 77.0 



25 



26 



27 



7 

 7 

 6 



29 

 51 

 55 



8 

 10 

 9 



44 

 68 

 70 



70.4 



4 



64.3 



5 



64.3 



6 



6 



33 



7 



46 



72.9 



28 



5 



59 



16 



80 



62.9 



7 



6 



30 



6 



42 



73.6 



29 



5 



53 



10 



68 



62.9 



8 



6 



27 



6 



39 



73.6 



30 



15 



41 



14 



70 



62.9 



9 



6 



26 



C 



38 



73.6 



31 



10 



40 



10 



60 



63.3 



10 



6 



24 



6 



36 



74.0 



32 



8 



50 



11 



69 



63.1 



11 



5 



24 



6 



35 



74.7 



33 



9 



42 



15 



66 



65.7 



12 



5 



22 



5 



32 



75.5 



34 



9 



42 



10 



61 



66.0 



13 



5 



24 



5 



34 



75.3 



35 



9 



40 



8 



57 



66.7 



14 



4 



19 



6 



29 



80.5 



36 



12 



44 



8 



64 



67.0 



15 



4 



34 



7 



45 



81.0 



37 



12 



39 



8 



59 



68.6 



16 



4 



19 



5 



28 



81.5 



38 



12 



38 



7 



57 



68.6 



17 



4 



27 



7 



38 



81.5 



39 



12 



40 



6 



58 



69.7 



18 



5 



20 



6 



31 



81.5 



40 



4 



29 



6 



39 



79.0 



19 



4 



26 



6 



36 



81.5 



41 



4 



25 



5 



34 



79.0 



20 



4 



24 



6 



34 



81.5 



42 



4 



23 



5 



32 



79.0 



21 



4 



23 



6 



32 



81.5 



43 



5 



28 



5 



38 



78.1 



22 



4 



23 



5 



32 



79.3 



44 



5 



30 



7 



42 



70.0 



Several specimens were reared from egg to adult in 28 days, and 

 this together with a preoviposition period of about 7 days would 

 give a possible complete life cycle from egg to egg of 35 days. This, 

 however, is a much shorter life cycle than normal, for in summer the 

 average length of the period from egg to adult, as shown in Table 7, 

 is between 30 and 40 days, and the preoviposition period may be 

 as short as 6 days in midsummer or, when the adult emerges in the 

 fall or early winter, as long as 123 or 148 days. In the vicinity of 

 Washington, D. C, there are between three and four generations a 

 year. 



RESISTANCE TO HIGH TEMPERATURES 



As already recorded by the writers (3), the granary weevil is not 

 very resistant to high temperatures. Exposure for a very few hours 

 to 115° F., for one hour to 118° to 120° F., or for 30 minutes to 

 130° F., will kill all stages. Moderately high temperatures also are 

 fatal to the granary weevil if maintained for any length of time. 

 Of adults placed in an incubator maintained at 95° F., four-fifths 

 died on the fifth day of exposure, a few survived for 9 days, and one 

 for 13 days. Little, if any, feeding occurred during this period and 

 no eggs were laid. Eggs incubated at 95° F. failed to hatch, and 

 larvse exposed to this temperature did not complete their develop- 

 ment. 



RESISTANCE TO LOW TEMPERATURES 



The granary weevil prefers a cool climate in which to breed and is 

 much more resistant to low temperatures than is the rice weevil. 



