Jan., 1924] PROGRESS OF AGRICULTURAL EXPERIMENTS 15 



the season's work. A screened house with a canvas roof was constructed 

 especially for these life-history studies. This was placed so that it has natural 

 shade. It proved successful in providing normal outdoor conditions where 

 detailed studies could be carried out accurately and conveniently. A soil 

 thermograph was installed and charts maintained throughout the season 

 showing the temperature of the soil six inches below the siu-face. A station 

 of Weather Bureau type was built, in which an air thermograph was placed, 

 together with other instruments. 



The infested material was brought to Durham before the close of the hiber- 

 nating season. From this material records were made showing the beginning 

 and the close of the pupal period for over- wintering larvae. It was found that 

 pupation began May 11 and continued until the close of July. A large number 

 of individual larvae were kept under observation. 



From these pupae records of emergence of adults were secured together with 

 data showing the length of the pupal period under New Hampshire conditions. 

 The pupal period for males was found to be about twenty days and that for 

 females about eighteen days. 



Emergence of adult moths from the over-wintering larvae began June 2. 

 and continued until the middle of August. Individual pairs of male and female 

 moths were observed and notes secured on the preoviposition period, as well 

 as the total longevity. The average life of the female moths from the over- 

 wintering generation was found to be about eighteen days and that of the male 

 moths about seventeen days. 



The eggs laid by the female moths were recorded. The average number of 

 eggs per moth was 451 ; the maximum number of eggs laid by a single individual 

 was 1003. 



In the course of this work it was found that a small percentage of over- 

 wintering larvae failed to pupate or to continue their development, although 

 remaining alive through the season. A somewhat larger percentage of pupae 

 failed to develop to adult moths, but all such pupae died. 



The eggs laid by the moths from the over- wintering generation were recorded 

 and kept under observation. The length of the egg stage was foimd to vary, 

 ranging from nine to twelve daj's, and this variation appears to be correlated 

 closely with the temperature records for the period. 



The larvae hatching from eggs described above constitute the second genera- 

 tion for the season; and these, in turn, were maintained under observation. 

 Complete data were secured as to the length of the larval period and the length 

 of time between molts. From these larvae further records were secured show- 

 ing the length of the pupal period of the second generation, the beginning and 

 end of the emergence period for adults, the length of the adult stage of the 

 second generation, the length of the egg stage for this generation and the 

 development of the larvae of the second generation, which, in turn, become 

 the over- wintering form for this species. It was definitely established that 

 in the locality of Durham the European Corn Borer can complete two genera- 

 tions in a year. This is in spite of the fact that the beginning of activity in 

 the spring occurs later than the corresponding development in Massachusetts 

 and in spite of the fact that development in the subsequent stages is delayed 

 under the climatic conditions prevailing at Durham. 



