280 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol, 14 



in the latter part of August and first half of September. The first 

 overwintering larvae hatched out above the eighth of September and 

 were in evidence until nearly the end of the month. The larvae fed 

 actively imtil cool weather when they plugged their entry holes in 

 preparation for hibernation. 



The chart above (Fig. 6) diagrams the life history as correlated 

 with the average temperatiu-e and humidity records of the station for 

 the season of 1920. 



Natural Enemies 



One very important hymenopterous parasite of P. ainsUei of the 

 family Bracomdae, genus Aleiodes, was reared. While boring insects 

 do not usually have natural enemies of sufficient importance to be con- 

 sidered as a factor in the control of the insect, this parasite will un- 

 doubtedly reduce the percentage of infestation during the coming 

 season. Fully fifty per cent of the larvae collected were parasitized, 

 each one having from four to eight Braconid larvae on it. 



CONCLUSiON 



The European Corn-Borer has two complete generations in Massa- 

 chusetts, which closely parallels the life history of P. ainsliei as worked 

 out at Ames. While each of the stages appeared a little later during 

 1920 at Ames than like stages appeared in the European Com Borer 

 in Massachusetts, this can no doubt be explained by the fact that 

 each was studied during different years, under varying degrees of tem- 

 perature conditions. Given similar conditions for each, it is the writ- 

 er's opinion that the tw^o insects would parallel each other in Iowa, 

 should P. nubilalis be introduced into the state. The problem before 

 us is a grave one, far reaching in its consequences, and no efforts should 

 be lost in the work to prevent the further spread of this pest. 



References 



1. Heinrich, C, Journ. Agr. Research, Vol. XVIII, No. 3, Wash. D. C, Nov. 

 1, 1919. 



2. Britton, W, E., Nineteenth Rep. State Ent., Bull. 218, Conn. Agr. Exp, 

 Sta., 1920. 



3. Flint, W. P., and Malloch, J. R., The European Corn Borer and Some 

 Similar Native Insects, Vol, XII, Art, X, Bull. 111. Nat. Hist. Survey, June 1920 



