﻿BULLETIN OF THE 



No. 8 



Contribution from the Bureau of Entomology, L. O. Howard, Chit- 

 September 27 1913. 



THE WESTERN CORN ROOTWORM. 



By F. M. Webster, 

 In Charge of Cereal and Forage Insect Investigations. 



INTRODUCTION. 



The western corn rootworm {Diabrotica longicornis Say) derives 

 its common name from the fact that the larva (fig. 1) was first 

 observed attacking the roots of corn in the Middle West, Its larval 

 habits, its life cycle, and the appearance of the adult insect (fig. 2) 

 are all entirely different from those of the southern corn rootworm 

 (Diabrotica duodecimpunctata Oliv.), though the worms themselves. 

 are exceedingly alike in appearance. In figure 1 the larva is ex- 

 tended at full length, as when feeding, having 

 been drawn from living individuals. 



The beetles (fig. 2) in life are about the size 

 of the striped cucumber beetle (Diabrotica 

 vittata Fab.), but smaller and less robust than 

 the southern corn rootworm, and are entirely 

 of a green or yellowish -green color, except the 

 eyes, which are black. The farmer will be 

 most likely to observe these feeding among 

 the silk of the 

 ears and the ^^M^ 

 pollen of corn 

 during late Au- 

 gust and Sep- 

 tember, though 

 the writer has 



seen them enter houses in the country at night, being attracted by 

 the evening lamps. An abundance of these beetles in a cornfield 

 should be a distinct warning that the field should not be planted to 

 corn the following year, but that it should be devoted to wheat, oats, 

 barley, rye, or to any crop other than corn. 



SEASONAL HISTORY. 



The eggs (fig. 3) are minute, yellowish-white objects, having to 

 the unaided eye much the appearance of minute grains of white sand. 



6135°— 13 



Fig. 1. — The western corn rootworm 

 (Diabrotica longicornis) : Larva, or 

 " worm." Much enlarged. (Origi- 

 nal.) 



Fig. 2. — The western corn 

 rootworm : Adult, or 

 beetle ; a, claw of hind 

 leg. Muc'i enlarged. 

 (Original.) 



