﻿32 ■ BULLETIN 13&3, U. S. DEPAETMENT OF AGRICULTURE 



varying from 61.5° to 68.5° F., the pupal stage lasted from 10 to 

 16 days. 



The developmental period from egg to adult may be completed in 

 28 days, which, with a preoviposition period of 7 days, makes pos- 

 sible a life cycle from egg to egg of 35 days. The normal egg-to- 

 adult cycle in summer is between 30 and 40 days, to which should 

 be added, in securing the egg-to-egg cycle, a period varying from 6 

 days m midsummer to 148 days if the adult happens to emerge dur- 

 ing the fall and hibernate as adult. There may be three or four 

 generations a year in the vicinity of Washington, D. C. 



The granary weevil is very resistant to low temperatures. Prac- 

 tically all of a large number of adults refrigerated at 30° to 35° F. 

 were found alive after one month, and a few survived for 73 days. 

 Adults exposed to a constant temperature of 15° F. survived only for 

 9 days, to 5° F. for 7^ hours, and to zero Fahrenheit for 5 hours. 

 Of eggs exposed to 30° F. for 28 days, 20 per cent survived. A few 

 larvae survived refrigeration at 30° F. for 44 days. 



The granary weevil is not very resistant to high temperatures. Ex- 

 posure for a few hours to 115° F. will kill all stages, and all stages 

 are killed within one hour when exposed to 118° to 120° F. Moder- 

 ately high temperatures are also fatal if maintained for any length 

 of time. At 95° F. four-fifths of the aduJts died on the fifth day of 

 exposure, and a few lived 9 days, and one for 13 days; little or no 

 feeding occurred and no eggs were laid. Eggs incubated at 95° F. 

 failed to hatch, and larvae exposed to this temperature did not com- 

 plete their development. 



The granary weevil in both larval and pupal stages is attacked by 

 several hymenopterous parasites. Although these may become very 

 numerous at times, they can not be depended upon for effective con- 

 trol, which can be secured only by heating the grain to a tempera- 

 ture of 125° F. or above, or by fumigation with standard effective 

 fumigants. 



LITERATURE CITED 



(1) Back, E. A. 



1919. Conserving corn from weevils in the Gulf Coast States. U. S. 

 Dept. Agr., Farmers' Bui. 1029, 36 pp., iUus. 



(2) and Cotton, R. T. 



1922. Stored-grain pests. U. S. Dept. Agr., Farmers' Bui. 1260, 47 pp., 



iilus. 



(3) 



1924. Relative resistance of the rice weevil, Sitophilus oryza L., and the 

 granary weevil, S. granarius L., to high and low temperatures. 

 In U. S. Dept. Agr., Jour. Agr. Research, vol. 28, pp. 1043- 

 1044. 



(4) Chapman, R. N. 



1921. Insects infesting stored food products. Univ. Minn. Agr. Exp. 

 Sta. Bui. 198, 76 pp., iUus. 



(5) 



1923. The possibility of transmitting a Calendra infestation from wheat 



to macaroni thru the processes of milling and inanufacturing. 

 In Jour. Econ. Ent., vol. 16, pp. 341-348, iUus. 



(6) Chittenden, F. H. 



1895. The more important insects injurious to ftored grain. In U. S. 

 Dept. Agr. Yearbook 1894, pp. 277-294 illus. 



(7) 

 (8) 



1896. Some insects injurious to stored grain. U. S. Dept. Agr., Farmers' 

 Bui. 45, 24 pp., illus. 



1896. Insects affecting cereals and other dry vegetable foods. In U. S. 

 Dept. Agr., Div. Ent. Bui. 4, n. s., pp. 112-130, illus. 



