INSECTS INJURIOUS TO MISCELLANEOUS CROPS 387 



in 1875 and has since spread northward along the Mississippi.* 

 In 1879 it was reported from Florida and was studied by Pro- 

 fessor J. H. Comstock.f 



The adult beetle is a rather slender insect, about one-quarter 

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

 thorax, 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 



FIG. 322. Present known distribution of the sweet-potato weevil in the 

 southern United States. (Farmers' Bulletin 1020). 



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 in the 

 course of the season, and with the aid of the beetles, they thor- 

 oughly 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 life cycle requires from thirty to forty days, so that there 

 may be several generations. in a year, Professor Comstock having 



* Bulletin 28, La. Agr. Exp. Sta., p. 999. 



t See Report U. S. Comm. Agr., for 1879, p. 249. 



