"weevil" IX GRAIN". 157 



build, being almost as broad as long. It soon devours the 

 soft interior of the kernel and then changes to a ])ui^a, 

 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 larva? injure the grain, but the beetles feed npon it, 

 and then hollow out a shelter for themselves within the 

 hull. The beetles are quite long-lived and thus do con- 

 siderable damage. The egg-laying pewod is equally long, 

 and as there are three or four broods in the Xorth and six 

 or more in the South, it has been estimated that the 

 progeny of one pair would amonnt 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 

 {Silvaniis stirinamensis Linn.) (Fig. 89). It is a cosmo- 

 politan pest and is also nearly omnivorons. 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 from that of 

 the Granary-weevil. Having six legs to cj^rry it about, it 

 is not satisfied with a single seed, but runs about here and 

 there, nibbling at several. When full-grown' the larva 

 glues together several grains or fragments into a little case, 

 and inside of this transforms to the pupa and then to the 

 beetle. In early spring this life-cycle requires from six to 

 ten weeks, but in summer it is reduced to about twenty- 

 five days. Thus there are from three to six or more 

 generations during a season, according to the latitude. 



