94 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 12 



plant which retards the development of the ear and in many cases pre- 

 vents proper fertilization through injury to the tassel. The ears are 

 also tunnelled by the larvae which enter by way of the pedicel or bore 

 directly through the husk and tunnel through the kernels and cob. 

 As many as fifteen full-grown larvae, each about an inch long, have 

 been found feeding upon and within a single ear of sweet corn. This 

 damage to the stalk and ears by the insect is often still further in- 

 creased by the ingress of various rots which reduce both stalks and ears 

 to a soft, putrid condition totally unfit for use as seed or for feeding to 

 stock. Actual field counts in a quarter-acre plot of sweet corn have 

 resulted in finding that 100 per cent of the ears were infested by larvae 

 of the European Corn Borer. Field counts made in badly infested 

 areas showed an average of 46 larvae per plant; or at the rate of about 

 1,050,000 per acre. 



The larvae of this generation reach full growth and pupate within 

 their host plant about the middle of July. The moths emerge about 

 the last week of July and deposit eggs for the second generation of 

 larvae on late corn or upon other wild or cultivated plants. The 

 habits of these second generation larvae in late corn are essentially the 

 same as for the first generation except that greater injury is sustained 

 by the ears. The larvae feed until their activities are halted by the 

 advent of severe winter weather in November or December. 



It will be noted then that there are two complete generations of the 

 European Corn Borer each year and that individual females in each 

 generation deposit an average of from 350 to 550 eggs each. This 

 enables the insect to increase its numbers very rapidly as its multi- 

 plication is practically unchecked by the activities of parasites or other 

 natural enemies. 



Danger of Widespread Injury to the Corn Crop 



Although the female of the European Corn Borer is capable of flight 

 and may gradually extend the limits of infestation by natural spread, 

 the chief element of danger in this respect is that infested plants or 

 plant products may be transported from the area now infested by the 

 insect to points outside of that area. 



Danger of Spread Through Transportation of Corn or Its Products 



The transportation of corn or its products offers perhaps the most 

 common means by which the insect may become widely disseminated. 



Sweet Corn or Roasting Ears. During the early summer season 

 considerable quantities of sweet corn are shipped north from the Bos- 

 ton wholesale market in order to take advantage of the early season 

 prices prevailing in northern Massachusetts, New Hampshire and 



