120 



APPLIED ENTOMOLOGY 



The Corn-root Worms. There are several species of the genus Diabrotica 

 which as larva? appear to make a specialty of feeding either upon the base of the 

 stem or the roots of corn. 



The Southern Corn-root worm or Twelve-spotted Cucumber beetle (Diabrot- 

 ica duodecimpunctata Oliv.) is found practically everywhere in the United States 

 east of the Rocky Mountains, but is usually a serious pest only from Maryland 

 to Florida and as far west as southern Ohio, Indiana and Illinois, Alabama, 

 Louisiana and Texas. The insect generally winters as the adult beetle (Fig. 108) 

 under rubbish or in other protected places, except in the far South where it is 



FIG. 108. F IG . 109. 



FIG. 108. Adult Southern Corn-root Worm (Diabrotica duodecimpunctata Oliv.), 

 enlarged about eight times. (From U. S. D. A. Farm. Bull. 950.) 



FIG. 109. Grub of Southern Corn-root Worm and its burrow in corn. Much en- 

 larged. (From U. S. D. A. Farm. Bull. 950.) 



more or less active during this period. In spring it lays its eggs just below ground, 

 on or near the young corn plants, and the tiny grubs which hatch, attack the corn, 

 feeding on the roots and drilling into the stem just above them, boring out the 

 crown and killing the bud (Fig. 109). From this habit the insect is often called 

 the " bud worm" or "drill worm." Small plants injured in this way break off 

 at the crowns when pulled, and larger ones become dwarfed and yellowish. 

 Other plants such as wheat, millet, alfalfa, etc., are also attacked by the larvse. 

 The adult beetle is about a quarter of an inch long, yellowish-green with black 

 head and legs and twelve black spots on its back. It feeds on squashes, cucum- 

 bers and many other plants. There appear to be two generations each year in the 

 North and three in the South, but most of the injury is caused by the first genera- 

 tion. Burning over waste places where there is rubbish, during the cold months 

 or on cold days will destroy many of the beetles which are seeking protection 



