INSECTS INJURIOUS TO THE SWEET POTATO 439 



inch long, of a bluish-black color, with a reddish-brown prothorax, 

 and has received its specific name, formicarius, from its fancied 

 resemblance to an ant. 



Life History. The yellowish-white, oval eggs are deposited 

 in small cavities eaten out by the mother beetle either at the 

 base of the vine or at the stem end of the tuberous root, or in 

 the tubers in storage. The small grubs commence to burrow 

 in the vine, sometimes maturing in the vine before any tubers 

 have developed, but usually they descend to the tubers, which 



FIG. 314. The sweet-potato root-borer (Cylas formicarius): extreme left 

 hand figure, adult beetle, with enlarged antennae at right; figure at 

 left center, pupa; at right center, larva; at extreme right, portion of 

 sweet-potato tuber channeled by borer all figures except the last con- 

 siderably enlarged; natural sizes indicated by hair lines. (After Far- 

 mer's Bulletin, No. 26, U. S. Dept. Agr.) 



in the course of the season, and with the aid of the beetles, they 

 thoroughly riddle. The full-grown larva is about one-quarter 

 inch long, whitish with light brown head, the segments are strongly 

 constricted, and the legs are wanting, being represented by mere 

 tubercles. The grub forms a small cavity at the end of the 

 burrow and transforms to the pupa. In this stage it remains from 

 one to two weeks, when the adult beetle emerges and after a few 

 days commences to lay eggs for another generation. The whole 



