THE COLEOPTERA 



121 



there. A careful crop rotation, never planting corn twice in succession on the 

 same land is also of value. Cotton, not being attacked by this pest is a safe crop 

 to follow corn and a legume is desirable in the rotation. The insect is most 

 serious in wet seasons and on low land. Corn is often more thickly planted on 

 low places on this account, to increase the chance of getting a stand. Fertiliza- 

 tion and cultivation increase the vigor and resistance of the plants to attack. 

 In the far South corn planted during April is more likely to be injured than that 

 planted before this time or after the tenth of May. 



The Western Corn-root worm (Diabrotica longicornis Say) occurs from 

 Nova Scotia to the Gulf of Mexico and west to Minnesota, Nebaska and New 

 Mexico, but is most injurious from Ohio 

 to Tennessee and from South Dakota 

 through Nebraska, Iowa and Missouri. 

 The winter is spent in the egg in the 

 ground and the grubs (Fig. 110) hatch 

 in the spring and attack the corn roots enlarged. 

 (Fig. Ill) but never the stem. After 

 feeding until full-grown they pupate in the ground and the adult beetles 

 emerge in July and August and lay their eggs. There is therefore, but 

 one generation a year. The adult beetles (Fig. 112) are about one-fifth 

 of an inch long and, except for their black eyes, are entirely greenish or 

 yellowish-green. They feed on the pollen and silk of corn and on the 



FIG. 110. Grub of Western Corn-root 

 worm (Diabrotica longicornis Say) , much 

 (From U. S. D. A. Bull. 8.) 



FIG. 111. FIG. 112. 



FIG. 111. Work of Western Corn-root worm in corn roots. (From U. S. D. A. 

 Bull. 8.) 



FIG. 112. Adult Western Corn-root worm, enlarged. Hair line at right shows 

 real length. (From U. S. D. A. Bull. 8.) 



blossoms and leaves of other plants, in August and September and if abundant 

 then in a corn field, one may be certain that that field will be well stocked with 

 eggs and therefore that corn should not be planted there again the following 

 spring Corn attacked by the grubs at first produces shortened ears with kernels 

 lacking at the tips: later it fails to produce the ears, and dwarfing of the plants 



