460 HYBEnNATIOX OF INSECTS. 



pidity and pass the winter ? In ray opioion, certainly 

 not. 



In the first place, if sensations proceeding from cold 

 lead insects to select retreats for hybernating, how 

 comes it that, as above shown, a large proportion of 

 them enter these retreats before any severe cold has 

 been felt, and on days considerably warmer than many 

 that preceded them ? Ifthis supposition have any mean- 

 ing, it must imply that insects are so constituted that, 

 when a certain degree of cold has been felt by them, 

 the sensations which this feeling excites impel them 

 to &8ek out hybernacula. Now the thermometer in 

 -the shade on the 14th of October 1816, when I observed 

 vast numbers thus employed, was at 58° — this then, on 

 the theory in question, is a temperature sufficiently 

 low to induce the requisite sensations. But it so hap- 

 pens, as I learn from my meteorological journal (which 

 registers the greatest and least daily temperature as 

 indicated by a Six's thermometer), that on the 3Ut 

 August 1816 the greatest heat was not more than 52', 

 or six degrees lower than on the I 1th of October : yet it 

 was six weeks Inter that insects retired for the winter ! 



But it m.ay be objected, that it is perhaps not so 

 much the precise degree of cold prevaiiing on the day 

 when insects select their hybernacula, that regulates 

 their movements, as the lower degree which may have 

 obtained for a few nights previously, and which may 

 act upon their delicate organization so as to influence 

 their future proceedings. Facts, however, are again in 

 direct opposition to the exj)lanation ; for I find that, 

 for a w^ek previously to the Uth of October 1816, the 



