456 HVBERNATION OF INSECTS. 



they reappear much earlier in forward than in backward 

 springs. Thus in the early spring of 1805 (to me a 

 memorable one, since in it I began my entomological 

 career, and had anxiously watched its first approaches 

 in order to study practically the science of which 1 had 

 gained some theoretical knowledge in the winter,) in- 

 sects were generally out by the middle of March ; and 

 before the 30th, I find, on referring to my entomologi- 

 cal journal, that! had taken and investignted (1 scarcely 

 need add, not always w ith a correct result) fifty-eight 

 coleopterous species : while in the last untoward spring 

 (1816) I did not observe even a bee abroad until the 

 20th of April ; and t^ie first butterfly that I saw did 

 not appear until tlie i'6th. 



There are, however, circumstances connected with 

 this revival, which seem to prove that something more 

 than the mere sensation of warmth is concerned in 

 causing it. I shall not insist upon the remarkable fact 

 which Spallanzani has noticed, that insects reappear 

 in spring at a temperature considerably lower than 

 that at w hich they retired in autumn ; because it may 

 be plausibly enough explained by reference to their in- 

 creased irritability in spring, the result of so long an 

 abstinence from food, and their consequent augmented 

 sensibility to the stimulus of heat. But if the mere 

 perception of warmth were the sole cause of insects re- 

 laxing from a state of torpidity, then we might fairly 

 infer, that species of apparently similar organization, 

 and placed in similar circumstances, would leave their 

 winter quarters at the same time. This, however, is 

 far from being the case. Reaumur observed that the 

 Jarvas of Papilio Cinxia quitted their nest a full month 



