HYBERNATIOX OF INSECTS. 531 



would not become torpid at all — at least this has proved the ftict witii 

 marmots and dormice thus treated ; and the Aphis of the rose (A. Rosa'), 

 which becomes torpid in winter in the open air ', retains its activity, and 

 gives birth to a numerous progeny, upon rose trees preserved in green- 

 houses and warm apartments. 



But can we, in the same way, regard mere cold as the cause of the hyber- 

 nation of insects ? Is it wholly owing to this agent, as most writers seem 

 to think — to feelings either of a pleasurable or painful nature produced 

 by it — that, previously to becoming torpid, they select or fabricate commo- 

 dious retreats precisely adapted to the constitution and wants of different 

 species, in which they quietly wait the accession of torpidity and pass the 

 winter? In my opinion, 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 jiro- 

 portion of them enter these retreats before any severe cold has been felt, 

 and on days considerably warmer than many that preceded them ? If this 

 supposition have any meaning, it must imply that insects are so constituted 

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

 which this feeling excites impel them to seek out hybernacula. Now the 

 t'lermometer 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 ques- 

 tion, is a temperature sufficiently low to induce the requisite sensations. 

 But it so happens, as I learn from my meteorological journal (which re- 

 gisters the greatest and least daily temperature as indicated by a Six's ther- 

 mometer), that on the 31st of August, 1816, the greatest heat was not 

 more than 52°, or six degrees lower than on the 14th of October : yet it 

 was six weeks later that insects retired for the winter! 



But it may be objected, that it is perhaps not so much the precise de- 

 gree of cold prevailmg on the day when insects select their hybernacula, 

 that regulates their movements, as the lower degree which may have ob- 

 tained for a few nights previously, and which may act upon their delicate 

 organisation so as to influence their future proceedings. Facts, however, 

 are again in direct opposition to the explanation ; for I find that, for a 

 week previously to the 14th of October, 1816, the thermometer was never 

 lower at night than 48°, while in the first week in August it was twice as 

 low as 46°, and never higher than 50°.^^ 



As a last resource, the advocates of the doctrine I am opposing may 

 u:ge, that possibly insects may even have their sensations affected by the 



1 Kyber, in Germar's Mag. der Eiit. ii. 3. 



2 Since the publication of the first edition of this volume, I have had an oppor- 

 tunity of making some observations which strongly corroborate the above reasoning. 

 The month of October in the year 1817 set in extremely cold. From the tirst to the 

 Cth, piercing north and north-west winds blew; the thermometer at Hull, though the 

 sun shone brightly in the day-time, was never higher than from 52° to oG*^, 

 nor at night than 38°; in fact on the 1st and 3d it sank as low as 34°, and on 

 the 2d to 31°: and on those daj-s, at eight in the morning, the grass was covered 

 with a white hoar frost; in short, to every one's feelings the weather indicated De- 

 cember rather than October. Here, then, was every condition fulfilled that the 

 theory I am opposing can require; consequently, according to that theory, such a 

 state of the atmosphere should have driven every hybernating insect to its winter 

 quarters. But so far was this from being the case, that on the 5th, when I made an 

 excursion purposely to ascertain the fact, I found all the insects still abroad which I 

 had met with six weeks before in similar situations. 



M M 2 



