90 
to the constitution, mode of life, and wants of the 
occupant.” 
«The degree of cold which insects in their dif- 
ferent states, while torpid, are able to endure is 
various.” The pupe of papilio brassicze, exposed to a 
cold fourteen degrees below the freezing point of 
Fahrenheit, became a lump of ice; yet were afterwards 
thawed, and produced butterflies. It is probable, 
however, that many do not survive even a less de- 
gree of cold. But Kirby argues from various and 
minute investigation, that although cold may be a 
cause of torpidity in many animals, in man for ex- 
ample, when exposed to a severe cold, yet it is not 
the immediate cause of hybernation ; for which, ani- 
mals begin to make careful provision in mild wea- 
ther, even such as have had no previous acquaint- 
ance with the cold season. “ What then,” says 
he, “ regulates these preparations? I answer, In- 
stinct.” 
“ We find torpidity,” says sir W. Jardine, Notes on 
White’s Selborne, “ occurring among various animals, 
fishes, the amphibia, reptiles, and insects; but we 
have never found any authenticated instance of this 
provision amongst birds.” 
What has been said of insects above may pro- 
bably apply to crustacea™. Certainly spiders and 
scorpions hide themselves, and fast, during the winter; 
» In the early part of spring, lobsters and crayfish, &c. change 
their shells. This is not effected, as I learn from an excellent 
naturalist, Mr. Dillwyn, by throwing off their old shells, but by a 
general deliquescence of the shelly matter. 
