INSECTS INJURIOUS TO STORED GRAINS 



177 



hatching from this is without legs, somewhat shorter than the adult, 

 white in color, and of a very robust build, being almost as broad 

 as long. It soon devours the soft interior of the kernel and then 

 changes to a pupa, from which the adult beetle emerges in about 

 six weeks from the time the egg was laid. 



Only a single larva inhabits a kernel of wheat, but several 

 will often be found in that of corn. Not only do the larvae injure 

 the grain, but the beetles feed upon it, and then hollow out a shelter 

 for themselves within the hull. The beetles are quite long-lived, 

 and thus do considerable damage. The egg-laying period is 

 equally long, and as there are three or four broods in the North 

 and six or more in the South, it has been estimated that the prog- 

 eny of one pair would amount to 6000 insects in a single season. 



Grain-beetles 



Another beetle very common in the granary, but of quite 

 different appearance, is the Saw-toothed Grain-beetle* (Fig. 151). 



cU 



FIG. 151. The saw-toothed grain beetle (Silvanus surinamensis) : a, adult 

 beetle; 6, pupa; c, larva all enlarged; . d, antenna of larva still more 

 enlarged; d, the red or square-necked grain beetle (Catkartus gemellatus 

 Duv.) (After Chittenden, U. S. Dept. Agr.) 



It is a cosmopolitan pest and is also nearly omnivorous. The 

 beetle is only about one-tenth of an inch long, very much flattened, 

 of a dark-brown color, and may be easily recognized by the six saw- 

 like teeth on each side of the thorax. The larva is of a dirty- 

 white color, and quite dissimilar to that of the granary weevil. 

 * Silvanus surinamensis Linn. Family Citcujidfe. 



