460 HYBERNATION OF INSECTS. 
pid in winter in the open air®, retains its activity and 
gives birth to a numerous progeny upon rose trees pre- 
served in greenhouses and warm apartments, — 
But, can we, in the same way, regard mere cold as 
the cause of the hybernation of insects? Is it wholly 
owing to this agent, as most writers seem to think—to 
feelings either of a pleasurable or painful nature pro- 
duced by it—that previously to becoming torpid they 
select or fabricate commodious 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? Ifthis 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 Oc- 
tober 1816, when I observed vast numbers thus employ- 
ed, was at 58°—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 me- 
teorological journal (which registers the greatest and 
_ least daily temperature as indicated by a Six’s thermo- 
- meter), that on the 31st of August 1816 the greatest 
* Kyber in Germar’s Mag. der Ent. ii. 3. 
