1917] Hibernation: A Periodical Phenome?ion 185 



Hymenoptera Lophyrus pint L, 



Symbols as above with addition of "p" for prepupa and numbers for alternating 

 generations and italicized to indicate injurious period. 



This method of tabulation is more easily read and used than the system some- 

 times employed by the U. S. Bureau in which a circle represents the whole 

 year and different stages occupy sectors or are shown by spiral lines. In a 

 life cycle that extended over several years, such a method would lead to 

 endless complications. 



For the Tortricids of European forests we find by compilation 

 that those species which feed on the outside of the tree hibernate 

 in a resistant stage that is, as eggs or pupae — whereas those 

 which feed on the inside (protected places) of the tree hibernate 

 as larvae. 



TABLE IV. 



Again compiling the data on the Noctuidae from the same 

 source similar results are obtained and it is also shown that 

 food supply is a factor in the determination of the hibernating 

 stage. 



