UNITED STATES DEPARTMENT OF AGRICULTURE 
f M|^ BULLETIN No. 1080 
^^^/^^•^-u 
Washington, D. C. 
July 22, 1S22 
EFFECT OF LOW TEMPERATURE ON THE HATCHING OF 
GIPSY-MOTH EGGS. 
By John N. Summers, 
Scientific Assistcnit. Gipsy-Moth and. Brotcn-Tail Moth Investigations, Bureau 
of Entomology. 
CONTENTS. 
Page. 
Intiodiiction 1 
Pieliminai-y discussion 1 
First investigations , 2 
Method of liandling all egg clusters 
used in experiments 3 
Monthly collections 3 
Months exposure 4 
Natural protection 4 
Artificial protection 4 
Exposures of clusters to one severe 
drop in temperature 5 
Page. 
Temperature resistance 5 
Summer survey of hatching 5 
Weather 6 
Results obtained from experiments- 6 
Results of summer survey of hatch- 
ing 9 
Eii't ctiveness of nonhatch 11 
Effects of cold on parasites 12 
Conclusions 13 
INTRODUCTION. 
Extensive study of the gips}^ moth {Porthetrla disyar 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 mam^ cases is the 
most valuable, acts upon the eggs and causes a failure to hatch. This 
phenomenon has been termed nonhatch. The results of several j^ears' 
study are presented in this bulletin. 
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 years ago the moth had not spread into territory having 
such low temperatures regularly. It is probable that even in the older 
infested area there Avere isolated pockets v\diich. owing to topog- 
raphy, attained temperatures low enough to kill. Likewise it is 
probable that a careful examination of some of the ^gg clusters which 
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