HYBERNATION OF INSECTS. 



365 



siderably below the freezing point to affect them. The 

 winter of 1813-14 was one of the severest we had had for many 

 years, Fahrenheit's thermometer having been more than once 

 as low as 8° when the ground was wholly free from snow ; 

 yet almost the first objects which I observed in my garden, 

 in the commencement of spring, were numbers of the cater- 

 pillars of the gooseberry-moth (Abraxas grossulariata), which, 

 though they had passed the winter with no other shelter than 

 the slightly projecting rim of some large garden-pots, were 

 alive and quite uninjured ; and these and many other larvae 

 never in my recollection were so numerous and destructive as 

 in that spring : whence, as well as from the corresponding fact 

 recorded, with surprise, by Boerhaave, that insects abounded 

 as much after the intense winter of 1709, during which 

 Fahrenheit's thermometer fell to 0°, as after the mildest 

 season, we may see the fallacy of the popular notion, that 

 hard winters are destructive to insects. 1 



But though many larvae and pupae are able to resist a 

 great degree of cold, when it increases to a certain extent, 

 they yield to its intensity and become solid masses of ice. 

 In this state we should think it impossible that they should 

 ever revive. That an animal whose juices, muscles, and 

 whole body have been subjected to a process which splits 

 bombshells, and converted into an icy mass that may be 

 snapped asunder like a piece of glass, should ever recover its 

 vital powers, seems at first view little less than a miracle ; 

 and, if the reviviscency of the wheel animal (Rotifer vulgaris) 

 and of snails, &c, after years of desiccation, had not made us 

 familiar with similar prodigies, might have been pronounced 

 impossible; and it is probable that many insects when 

 thus frozen never do revive. Of the fact, however, as to 

 several species, there is no doubt. It was first noticed by 

 Lister, who relates that he had found caterpillars so frozen, 

 that when dropped into a glass they chinked like stones, 

 which nevertheless revived.' 2 Beaumur, indeed, repeated 

 this experiment without success ; and found that when the 



1 Vid. Spence in Transactions of the Horticult. Soc. of London, ii. 148. Com- 

 pare Reaum. ii. 141. 



2 Lister, Goedart, De lnsectis, 76. 



