INSECTS INJURIOUS TO STORED GRAINS 



191 



quite generally distributed. " The caterpillars form cylindrical 

 silken tubes in which they feed, and it is in great part their habit 

 of web-spinning that renders them so injurious where they obtain 

 a foothold. Upon attaining full growth the caterpillar leaves 

 its original silken domicile and forms a new web, which becomes 

 a cocoon in which to undergo its transformations to pupa and 

 imago. It is while searching for a suitable place for transforma- 

 tion that the insect is most troublesome. The infested flour 

 becomes felted together and lumpy, the machinery becomes 

 clogged, necessitating frequent and prolonged stoppage, and result- 

 ing in a short time in the loss of thousands of dollars in large 

 establishments . ' ' 



The life cycle of 

 this insect requires 

 ordinarily about 

 two months, but 

 may be completed 

 in thirty-eight days 

 under the most 

 favorable condi- 

 tions. The adult 

 moth measures a 

 little less than an 



inch across the expanded wings. The fore-wings are of a lead- 

 gray color, with transverse black markings, while the hind- 

 wings are dirty whitish, with a darker border. 



The Indian Meal-moth * (Fig. 140) larvae resemble those of 

 the grain-beetles in having a special liking for the embryo of 

 wheat-grains. They spin a fine silken web as they go from seed 

 to seed, to which they become attached, and to which is added a 

 large amount of excrement, thus spoiling for food much more 

 grain than is actually injured. 



The moth has a wing-expanse of an inch; the inner third 

 of the fore-wings being a whitish gray, and the outer portion 

 reddish-brown, with a coppery lustre. 



* Plodia interpunctcllu Hbn. Family Pymlidos. 



FIG. 141. The meal snout-moth (Pyralisfarinalis): 

 a, adult moth; b, larva; c, pupa in cocoon twice 

 natural size. (After Chittenden, U. S. D. Agr.) 



