482 Phylum Arthropoda 



They are very similar in their habits and look very much alike. The 

 granary weevil is the larger of the two species, is chestnut brown or 

 blackish in color, and has no functional wings. The rice weevil is smaller, 

 brownish in color with four light spots on the wing covers, and is an 

 active flier. 



The larvae of both the rice and the granary weevils live throughout 

 their entire life within the kernel, and are not ordinarily capable of a 

 free existence outside the kernel. The adult female, before laying her 

 eggs, bores a small hole in the grain berry with her mandibles, then turns 

 about and lays in it an egg which she covers with a gelatinous fluid that 

 seals the hole. In warm weather the granary weevil requires about 4 to 

 5 weeks to complete its development from egg to the adult weevil, while 

 the rice weevil may complete its development in 26 to 30 days. 



Granary or rice weevils may be raised in large quantities, with but 

 little care, in large-mouthed glass containers of about a gallon capacity. ' 

 This type of jar has a diameter slightly less than the height. A screen 

 wire cover or heavy muslin is used to keep the beetles in while allowing 

 a certain amount of air circulation. 



The jar is filled about % full of wheat, or wheat and corn, of a 

 moisture content of 14 to 15%, the optimum moisture level for weevil 

 infestation. It is often necessary to moisten wheat somewhat for culture 

 purposes because, when well dried for storage, wheat has a moisture con- 

 tent of only n to 13%. When exposed in a dry laboratory the moisture 

 content may go as low as 9%. A culture of adult weevils is placed with 

 the grain and the jar allowed to remain at a temperature of about 23 

 to 2 6° C. Eggs will be laid in the grain, and in about 4 to 6 weeks 

 adults of the first generation of beetles will appear. After the culture 

 is strong enough, hundreds of weevils may be removed every day with 

 no decided reduction in population. The beetles may be removed by 

 scraping them off the inside of the glass jar or sifting them through a 

 No. 10 wire sieve, which allows the weevils to pass through, but retains 

 most of the wheat. 



After a time all the wheat will be riddled, with nothing but the husk 

 left, and much finely ground powder will collect on the bottom of the 

 jar; also, if the culture becomes too densely populated, much metabolic 

 water accumulates within the jar, whereby the contents may become a 

 soggy mass. Before this happens the weevils should be separated from 

 the grain and placed in a jar containing fresh clean grain, thus starting 

 the culture over again. By keeping 3 or 4 jars going at the same time 

 a continuous supply of beetles will always be on hand in the laboratory. 



If beetles of a certain age are required, a large number of adults 

 may be placed in clean grain for 2 or 3 days and then removed. The 

 eggs laid by the adults will hatch and after a time, depending upon the 



