INSECTS INJURIOUS TO CORN. 29! 



a time these larvae become too large for the small stem of the timothy, 

 and much more so for the bliiegrass, and they then eat their way out 

 of the grass stem and crawl about in search of some other plant that 

 will afford them a larger stem in which to mine. 



It is at this time that the larvae will enter the corn field, the corn 

 being from two inches to ten inches in height, and the larvae then crawl 

 up the stem a short distance and make a hole through it, and mine up- 

 wards in the middle of the stalk. This, of course, causes the same dam- 

 age to the corn as the burrowing of the larva in the stalk of grass did, 

 viz., to cause the corn above the point of entrance to wither and dry 

 up, turn white and die, and perhaps fall over, breaking off at the point 

 where the larva entered. One of these larvae is shown inside of a stalk 

 with the opening through which it entered in figure 48, c. 



The larvae may leave the corn plant by eating a hole through the 

 stem above the one through which it entered, and pass to another corn 

 plant, burrowing in it the same as before described. These larvae, when 

 full grown, are very apt to mine down below the original point of en- 

 trance and there transform to the pupae stage. If, therefore, the upper 

 and dead or injured portion of the stalk breaks off and falls to the 

 ground, the pupae are still left in the healthy, or at least standing, stalk. 

 A pupae is represented in figure 48, e. 



The larv-ae become full grown about the last of July, and the adults 

 appear from the middle of August through September and into October. 

 These adults are handsome moths of a mouse or fawn gray color, with 

 the outer third of the wings lighter, and a light or almost white band 

 separating the two regions. One of these moths is shown in figure 48, a. 



So far as is know^n, these moths do not lay their eggs in anything 

 but grass. There is but one brood of these insects a year, the winter be- 

 ing passed in the tgg stage, hence there is no danger of a corn field be- 

 coming widely infested with these insects, and this accounts for the fact 

 that the insect rarely is found distributed over an entire field of con- 

 siderable size. This stalk-borer, while feeding normally upon timothy 

 and bluegrass for its early larval existence, is forced, as it becomes too 

 large for the stalks of these plants, to seek other plants with larger stems, 

 and in doing so, the larvae will infest wheat and oat fields, as well as 

 corn, and will also burrow in potatoes, rhubarb, tomatoes, spinach, 

 blackberry and raspberry canes near the tip, cockle-bur, rag-weed, bur- 

 dock, almost all kinds of garden flowers, and also in the new growth of 

 currant, peach, apple, grape, and willow stems. In fact, these insects 

 seem to have no especial preference for any one plant, or even any par- 



