HYBERNATION OF INSECTS. 



35? 



perfect insects are females, which, not having been impreg- 

 nated, 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 benumb- 

 ment takes place ; but the insect, 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 no 

 need of a supply of air 1 ; its nutritive secretions cease ; no 

 more food is required ; 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 anima- 

 tion into the stiffened animal : if disturbed, its limbs and an- 

 tennae resume their power of extension, and even the facility 

 of spirting out their defensive fluid is re-acquired by many 

 beetles. 2 But however mild the atmosphere in winter, the 

 great bulk of hybernating insects, as if conscious of the de- 

 ceptions nature of their pleasurable feelings, and that no food 

 could then be procured, never quit their quarters, but quietly 

 wait for a renewal of their insensibility by a fresh accession 

 of cold. 



On this head I have had an opportunity of making some 

 observations which, in the paucity of recorded facts on the 

 hybernation of insects, you may not be sorry to have laid 

 before you. The 2d of December 1816 was even finer than 

 many of the preceding days of the season, which so happily 

 falsified the predictions that the unprecedented dismal sum- 

 mer would be followed by a severe winter. The thermometer 

 was 46° in the shade; not a breath of air was stirring; and 

 a bright sun imparted animation to troops of the winter gnat 

 ( Trichocera hiemalis), which frisked under every bush ; to 

 numerous PsycliodcE ; and even to the flesh-fly, of which two 

 or three individuals buzzed past me while digging in my 



1 Spallanzani, Rapports de V Air, &c, i. 30. 



2 Schmid in Illig. Mag. i. 222. 



A A 3 



