442 HYBERNATION OF INSECTS. 
this rule. Thus Aphis Rose, Cardui, and probably many 
others of the genus, hybernate both in the egg and per- 
fect state?; Papilio Cardui, Rhamni, and some other 
species, usually in the pupa, but often in the perfect 
state also; and Papilio Io, according to the accurate 
Brahm, in the three states of egg, pupa, and imago®. 
It is probable that in these instances the perfect insects 
are females, which, not having been impregnated, have 
their term of life prolonged beyond the ordinary period. 
The first cold weather, after insects have entered their 
winter quarters, produces effects upon them similar to- 
those which occur in the dormouse, hedgehog, and 
others of the larger animals subject to torpor. At first 
a partial benumbment takes place; but the imsect if 
touched is still capable of moving its organs. But as 
the cold increases all the animal functions cease. ‘The 
insect breathes no longer, and has ne need of a supply 
of air®; its nutritive secretions cease, and no more food 
is required; the muscles lose their irritability’; and it 
has all the external symptoms of death. In this state it 
continues during the existence of great cold, but the 
degree of its torpidity varies with the temperature of the 
atmosphere. The recurrence of a mild day, such as 
we sometimes have in winter, infuses a partial animation 
into the stiffened animal: if disturbed, its limbs and an- 
tennee resume their power of extension, and even the 
faculty of spirting out their defensive fluid is re-acquired 
by many beetles®. But however mild the atmosphere in 
@ Kyber in Germar Magazin der Entomologie, ii. 2. 
bilns. Kal. 188. ¢ Spallanzani, Rapports del Air, &c. i. 30. 
4 Carlisle in Phil. Trans. 1805, p. 25. 
¢ Schmid in Illig. Mag. i. 222. 
