June, '22] Crawford & spencer: European corn borer 223 



The male moths lived in confinement for from 6 to 21 days, averaging 

 13 days, while the females lived for from 10 to 31 days, averaging 17.4 

 days, with a pre-oviposition period (20 females) of from 3 to 9 days, 

 averaging 4 days. After this pre-oviposition period they laid from 

 95 to 988 eggs per female, at the rate of from 12-231, an average of 

 75.3 eggs per day, m masses containing from 1-64 eggs, an average of 

 33 per mass. All of the eggs kept under observation hatched. The 

 duration of this stage was from 3 to 8 days, averaging for the period 

 between June 28th and August 2d 4.71 days. 



In the field a study of the incidence of egg laying on com planted on 

 May 31st in a field adjacent to the northern margin of an old com patch 

 of 1920 at this time in oats and barley, was started. The moths began 

 to emerge on June 18th from the old stubble in the standing grain, 

 and eggs were not foimd until July 1st when 5 masses were secured from 

 100 plants though a most careful search was maintained in the inter- 

 vening period of 14 days; on July 3d 15 masses were secured on ap- 

 proximately 200 plants, at which time egg laying was becoming general 

 and some masses were observed to be hatching. The corn at this time 

 was from 9-20 inches high. No eggs were laid until the com averaged 

 about 15 inches in height. In the interval the adults were, without 

 doubt, flying southwest to another field planted on May 18th, which at 

 this time was markedly in advance of the field under observation in 

 development and finally suffered a loss of 65%. The field under 

 study on the north, however, was but 63.2% infested and the loss would 

 not exceed 5%. 



The first eggs taken in the season, however, were found in the field 

 June 21st and by July 5 hatching was general and the infestation was 

 showing up very clearly on the unrolling leaves where the newly hatched 

 larvae were feeding at the base. The evidence of attack became clearly 

 marked in the first week in July and by the second week the tassels were 

 falling on the early planted flint and sweet com. As the plant increased 

 in length and the larvae on the rolled up leaves were exposed to light, 

 they bored into the stalks, which by the end of July in the early planted 

 com began to break over. 



By the third week in July in the very early sweet com, and to a much 

 less extent in the flint, the majority of the larvae were full grown. 

 At that time a very small second brood developed in the very earliest 

 planted sweet corn, involving but a fraction of one percent of the 

 larvae. In this sweet corn 10 pupae in all were collected between July 

 21st and 26th and 4 pupae were secured from larvae collected at the same 

 time. From these pupae, after a period of 13 days, 2 male moths and 



