532 HYBERtfATION OF INSECTS. 



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 pre- 

 viously to their actual occurrence. But once more I refer to my meteoro- 

 logical journal ; and I find that the average lowest height of the thermo- 

 meter, in the week comprising the latter end of October and beginning o{ 

 November, 1816, was 43f ; while in the week comprising the same days 

 of the month of the end of August and beginning of September it was only 

 445.0 a difference surely too inconsiderable to build a theory upon. 



I have entered into this tedious detail, because it is of importance 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 determination to explain everything, led to promulgate. 

 But in truth there was no absolute need for imposing this fatigue upon 

 your attention ; for the single notorious consideration that in this climate, 

 as well as in more southern ones, we not unfrequently have sharp night- 

 frosts in summer, and colder weather at that season than in the latter end 

 of autumn and beginning of winter, and yet that insects do hybernate at 

 the latter period, but do not at the former, is an ample refutation of the 

 notion that mere cold is the cause of the phenomenon. If, indeed, the 

 hybernacula of insects were simply the underside of any dead leaf, clod, 

 or stone that chanced to be in the neighbourhood of their abode, it might 

 still be contended, that such situations were always resorted to by them 

 on the occurrence of a certain degree of cold, but that they remained in 

 them only when its continuance had induced torpidity ; and it seems to 

 have been in this view that most reasoners on this subject have regarded 

 the hybernation of the larger animals, to which they have exclusively di- 

 rected their attention. But had they been acquainted (as surely the 

 investigators of such a question ought to have been) with the economy of 

 the class of insects, in which not merely a few species as among quadru- 

 peds, but one half or three fourths of the whole, in our climates, hybernate, 

 they would have known that their hybernacula are in general totally dis- 

 tinct from their ordinary retreats in casual cold weather ; and that many of 

 them even fabricate habitations requiring considerable time and labour, ex- 

 pressly for the purpose of their winter residence which last fact in par- 

 ticular, on their theory, admits of no satisfactory explanation. We may 

 say, and truly, that the sensation of fatigue causes man to lie down and 

 sleep ; but we should laugh at any one who contended that this sensation 

 forced him first to make a four-post bedstead to repose upon. 



In the second place, if we grant for a moment that it is cold which 

 drives insects to their hybernacula, there are other phenomena attending 

 the state of hybernation, which, on this supposition, are inexplicable. If 

 cold led insects to enter their winter quarters, then they ought to 

 be led by the cessation of cold to quit them. But, as has been before 

 observed, we have often days in winter milder than at the period of hyber- 

 nating, and in which insects are so roused from their torpidity as to run 

 about nimbly when molested in their retreats ; yet, though their irritability 

 must have been increased by a two or three months' inactivity and absti- 

 nence, they do not leave them, but quietly remain until a fresh accession of 

 cold again induces insensibility. 



In short, to refer the hybernation of insects to the mere direct influence 

 of cold, is to suppose one of the most important acts of their existence 

 given up to the blind guidance of feelings which in the variable climates of 



