HYBERNATION OF INSECTS. 44-7 



in my recollection were so numerous and destructive as 

 in that spring : whence, as well as from the correspond- 

 ing fact recorded with surprise by Boerhaave, that in- 

 sects 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 \ 



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 pro- 

 cess 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 ( Vorticella rotatoria), and of snails, &c. 

 after years of desiccation, had not made us familiar with 

 similar prodigies, might have been pronounced impos- 

 sible ; and it is probable that many insects when thus 

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

 veral 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 ^. Reaumur, indeed, re- 

 peated this experiment without success ; and found that 

 when the larvae of Lasiocampa Pityocampa were frozen 

 into ice by a cold of 15° R. below zero (2° F. below 



* Vid. Spence in Transactions of the HorticuU. Soc, of London, ii. 

 148. Compare Reaum. ii. 141. 

 '' Lister, Goedart. de Insectis, 76. 



