BROAD-]SrOSED GRAIN WEEVIL. 3 



LIFE HISTORY (PL I).^ 



The adults of the broad-nosed grain weevil possess functional 

 v/ings, and although not great fliers they are capable of making short 

 flights in search of food. They fly to the cornfields in the summer, 

 feed on the grain, and deposit eggs in it before it becomes fully 

 hardened. 



The damaged and exposed ears of corn are the ones that are 

 attacked by the weevils, those ears that have a well-developed and 

 tightly fitting shuck being entirely immune from attack. 



After the grain is harvested and placed in storage the work of 

 <iestruction continues. The kernels infested in the field are com- 

 pletely destroyed, and the multiplying weevils attack cracked and 

 broken kernels and grain that is softened by excess moisture or is 

 damaged by the depredations of other grain pests. 



OVIPOSITION. 



Under favorable conditions oviposition occurs more frequently dur- 

 ing the hours of the morning; eggs are laid, however, at all times of 

 the day. 



The female weevil excavates the egg cavity in a manner very 

 similar to that of SitopMlus oryza. The weevil places herself in the 

 desired position. The sharp hook or claw on the end of the tibia of 

 each leg is dug into the surface of the kernel, the four legs thus form- 

 ing pivots on which the body oscillates. This oscillating movement 

 of the body, together with a turning movement of the head, imparts 

 to the proboscis a combined up-and-down and rotary motion. The 

 position of the legs is not changed, as a rule, until the excavation is 

 completed, and the proboscis or beak is seldom withdrawn during 

 this time. Work on the cavity continues until its depth approxi- 

 mates the length of the beak from the tip to the eyes. The sides are 

 then smoothed off. 



After the completion of the cavity the weevil reverses her position 

 and places the tip of her abdomen over the mouth of the egg cavity. 

 After a period of from two to three minutes the egg is ejected from 

 the ovipositor into the cavity, followed by .a liquid secretion that 

 forms a cap and cements the egg into place. This secretion quickly 

 hardens. Immediately after the egg is deposited the weevil turns 

 about and tamps down the edges of the egg cap with her beak, 

 picking up small pieces of the borings from the excavation and tamp- 

 ing in around the edges. 



The egg cap is transparent, and the outer surface is invariably 

 exactly level with the surrounding surface of the corn. After the 

 young larva has emerged from the egg and the egg cavity is filled 

 with larval borings it is often difficult to detect the original position 

 of the egg. 



' la breeding experiments frdm which the lite-history data were taken com was used as the host seed. 



