HYBERNATION OF INSECTS. 565 



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 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, previoushj to becoming torpid, they select or fabricate commodi- 

 ous 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 

 proportion 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 that, 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 thermometer in the shade on the 14th of October, 1816, when 

 I observed vast numbers thus employed, was at 53° : — this, then, on the 

 theory in question, is a temperature sufficiently low to induce the requisite 

 sensations. But it so happens, 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 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 

 degree of cold prevailing 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 deli- 

 cate organization so as to influence their future proceedings. Facts, how- 

 ever, 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 

 urge, that possibly insects may even have their sensations affected by the 

 cold some days before it comes on, in the same way as wc know that 

 spiders and some other animals are influenced by changes of weather 

 previously to their actual occurrence. But once more I refer to my mete- 



' Kylier, in Germar's Mas;, der Eut. ii. 3. 



* S nee the publication of ihe first, edition of this volume. I have had an opportunity of 

 making some obs3rvations which stron^rly conoborale the above reasoning. The month of 

 October in the year 1817 set in extremely cold. From the first to the tiih, piercing north 

 and north-west winds blew ; the ihcrmometcr at Hull, though the sun shone brightly in the 

 day-lime, was never higher than from bl'^ to 51")^, nor at night than oS-* ; in fact, on the 

 1st and 3d it sunk as low as Sl"^, and on the 21 to 31'^ : and on those days, at eight in the 

 morning, the grass was covered with a white hoar fro^i ; in .^hurt, to every one's feeling.? 

 the weather indicated December rather than O.-iober. lieie, then, was every coiuiiiion ful- 

 filled that the theory I am opposing can reiviire ; consecpienily. afcording lo ihnt theory, 

 such a state of the aimospliere shoiilil have driven every liyliernating insect to its winter 

 quarters. B'.it so far was this from being the case, that (»ii the 5th. wiieii I made an excur- 

 sion purposely to ascertain the fai;t I found all the insects blill abroad which I had met 

 with SIX weeks before in similar situations. 



48 



