UNITED STATES DEPARTMENT OF AGRICULTURE 



IMf BULLETIN No. 1080 IMf 





■sy^^'^^c 



Washington, D. C. 



July 22, IS 22 



EFFECT OF LOW TEMPERATURE ON THE HATCHING OF 

 GIPSY-MOTH EGGS. 



By John N. Summees, 



Scientific Assistant, Gipsy-Moth and Broion-Tail Moth Investigations, Bureau 



of Entomology. 



CONTENTS. 



Page. 



Introduction 1 



Preliminary discussion 1 



First investigations , 2 



Method of liandling all egg clusters 



used in experiments 3 



Monthly collections 3 



Month's exposure 4 



Natural protection 4 



Artificial protection 4 



Exposures of clusters to one severe 



drop in temperature 5 



Page. 



Temperature resistance o 



Summer survey of hatching 5 



Weather 6 



Results obtained from experiments- 6 

 Results of summer survey of hatch- 

 ing 9 



Effectiveness of nonhatch 11 



Effects of cold on parasites 12 



Conclusions 13 



INTRODUCTION. 



Extensive study of the gipsy moth {Porthetria dispar L.), made 

 in connection with the introduction, establishment, and dispersion 

 of its parasites, has shown that in New England there are agencies 

 of natural control responsible for a considerable mortality among the 

 various stages. 



One of these natural-control agencies, which in many cases is the 

 most valuable, acts upon the eggs and causes a failure to hatch. This 



phenomenon has been termed nonhatch. 

 study are presented in this bulletin. 



The results of several years' 



PRELIMINARY DISCUSSION. 



The failure of gipsy-moth eggs to hatch has been common enough 

 to attract attention during the last few years only. As will be shown 

 later, very low temperatures are responsible for this killing, and until 

 about 10 3^ears ago the moth had not spread into territory having 

 such low temperatures regularly. It is probable that even in the older 

 infested area there were isolated pockets Avhich, owing to topog- 

 raphy, attained temperatures low enough to kill. Likewise it is 

 probable that a careful examination of some of the egg clusters which 



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