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mosquitoes. Lister states that he has found cater- 

 pillars so frozen, that, when dropped into a glass, they 

 clinked like stones, and yet revived. Mr. William 

 Stickney, of Holderness, exposed some of the larvae 

 of the tipula oleracea to a severe frost, which con- 

 gealed them into ice : when fractured, their whole 

 interior was found to be frozen yet several of these 

 were re-animated. Bonnet exposed the pupae of 

 papilio brassicce to a cold amounting to zero of Fahren- 

 heit : they became masses of ice, yet produced but- 

 terflies. Spallanzani made the curious observation, 

 that insects re-appear in spring at a temperature con- 

 siderably lower than that at which they retired in 

 autumn. Agreeable to what has been mentioned, it 

 is to be regretted that authors have not discriminated 

 " between the state in which animals pass the winter, 

 and their selection of a situation in which they may 

 become subject to that state." 



There can be no doubt that a continued artificial 

 warmth would prevent many animals from entering 

 into a state of torpidity ; and the insect so destruc- 

 tive to the favourite of our flowers, the aphis rosce, if 

 exposed in winter to the inclemency of the season, 

 becomes torpid, while in the greenhouse it preserves 

 an active and animated being. It cannot be owing 

 to any effect of cold previously felt, that they are in- 

 duced to make preparation for their long repose : it 

 must be by a law of their being, imposed by Provi- 

 dence, " that, previously to becoming torpid, they 

 select or fabricate commodious retreats, precisely 

 adapted to the constitution and wants of different 

 species, in which they quietly wait the accession of 

 torpidity, and pass the winter." It has been very 

 properly remarked, that the fact of insects hyber- 

 nating at the close of autumn, and their not doing 



