366 



HYBERNATION OF INSECTS. 



larvae of Cnethocampa Pityocampa were frozen into ice by a 

 cold of 15° E. below zero (2° F. below zero), they could not 

 be made to revive. 1 But other trials have fully confirmed 

 Lister's observations. My friend Mr. Stickney, before men- 

 tioned as the author of a valuable Essay on the Grub (larva 

 of Tipula oleracea) — to ascertain the effect of cold in de- 

 stroying this insect, exposed some of them to a severe frost, 

 which congealed them into perfect masses of ice. When 

 broken, their whole interior was found to be frozen. Yet 

 several of these resumed their active powers. Bonnet had 

 precisely the same result with the pupae of Pontia Brassicce, 

 which, by exposing to a frost of 14° R. below zero (0° F.), 

 became lumps of ice, and yet produced butterflies 2 ; and in 

 an experiment made during Sir John Ross's voyage on the 

 caterpillars of a moth (Laria Rossii) two of them revived, and 

 one assumed the imago state, after being four times in suc- 

 cession exposed to a cold of 40° below zero, and four times 

 revivified by being brought into the warm atmosphere of the 

 cabin. Indeed, the circumstance that animals of a much 

 more complex organisation than insects, namely, serpents and 

 fishes, have been known to revive after being frozen, is suf- 

 ficient to dispel any doubts on this head. John Hunter, 

 though himself unsuccessful in his attempts to reanimate 

 carp and other animals that had been frozen, confesses that 

 the fact itself is so well authenticated as to admit of no ques- 

 tion. 3 



On what principle a faculty so extraordinary and so con- 

 trary to our common conceptions of the nature of animal life 

 depends, I shall not attempt to explain. Nor can any thing 

 very satisfactory be advanced with regard to the source of 

 the power which many insects in some states, and almost all 

 in the egg state, have of resisting intense degrees of cold 

 without becoming frozen. It is clear that the usual ex- 

 planation of the same faculty to a less degree in the warm- 

 blooded animals — the constant production of animal heat 

 from the caloric set free in the decomposition of the respired 

 air — will not avail us here. For, many large larvae, as 



1 Reaum. ii. 142. 2 CEuvres, vi. 12. 



3 Observations on the Animal Economy, 99. 



