372 



HYBERNATION OF INSECTS. 



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

 precise degree of cold prevailing on the day when inseets 

 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 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 0 . 1 



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 we 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 meteorological journal; and I find that the average 

 lowest height of the thermometer, in the week comprising 

 the latter end of October and beginning of November, 1816, 

 was 43y° ; while in the week comprising the same days of the 

 month of the end of August and beginning of September it 

 was only 44^° — a difference surely too inconsiderable to 

 build a theory upon. 



I have entered into this tedious detail, because it is of im- 

 portance- to the spirit of true philosophising to show what 

 little agreement there often is between facts and many of the 

 hypotheses which authors of the present day are, from their 



1 Since the publication of the first edition of this volume, I have had an 

 opportunity of making some observations which strongly corroborate the above 

 reasoning. The month of October in the year 1817 set in extremely cold. 

 From the 1st to the 6th, piercing north and north-west winds blew; the ther- 

 mometer at Hull, though the sun shone brightly in the day-time, was never 

 higher than from 52° to 56°, nor at night than 38° ; in fact, on the 1st and 3d 

 it sunk as low as 34°, and on the 2d to 31° : and on those days, at eight in the 

 morning, the grass was covered with a white hoar frost ; in short, to every one's 

 feelings the weather indicated December 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. 



