532 . HYBERNATION 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- 
fogital journal; and I find that the average lowest height of the thermo- 
meter, in the week comprising the latter end of October and beginning of 
November, 1816, was 431°; while in the week comprising the same days 
of the month of the end of August and beginning of September it was only 
445° — a difference surcly too inconsiderable to build a theory upon. 
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 
