184 
spring following the severe season just 
referred to I found that nearly all these 
larvae that had passed the winter out 
doors about the apple trees were dead, a 
circumstance I have never observed at 
any other time. The fact that this mor- 
tality was not due to parasites, that there 
was no Climatic peculiarity during that 
winter other than the cold, especially as 
the larvae in cellars and kitchens were 
healthy and lively, points strongly to 
the severe cold as the cause of this wel- 
comed mortality. If this inference is 
correct, we must conclude that insects 
which freeze up in winter may succumb 
to very severe cold. 
Farmers long that 
clover sward ploughed in autumn, and 
planted to corn the following spring, 
was less liable to be attacked by cut- 
worms, than when ploughed in spring, 
and immediately planted. This has led 
to the very general belief among farmers, 
which view is adopted by several noted 
entomologists, that exposure to the cold, 
especially to alternate freezing and thaw- 
ing, is what destroys the cut-worms. 
During the very severe winter already 
referred to, I subjected some cut-worms— 
larvae of species of Agrotis— to intense 
cold, and to alternate cold and _ heat, 
which seemed in no wise to injure them. 
Others were exposed very much as they 
would be by fall ploughing, and yet 
passed the winter in safety. The farmers 
are doubtless correct in thinking that fall 
since observed 
ploughing is a protection against these 
marauding cut-worms; but wrong in 
their explanation. Exposure to insect- 
ivorous birds and not to cold is the more 
probable solution, especially as frequent 
cultivation of the land in autumn and 
PSt CH, 
spring, when birds are plenty, is found 
to greatly augment the destruction of 
insects. 
The late Mr. Quinby, inhis work on bee 
keeping, states that the larva of the bee- 
moth, Galleria cereana, cannot survive 
exposure to the cold; that if these lar- 
vae are removed from the hive and its 
genial heat, during the winter, they 
surely die. Mr. G. M. Doolittle reports 
that he has observed these bee-moth 
caterpillars in exposed positions, and 
that they have survived even the present 
rigorous winter of 1880 and 81. I have 
often noticed these larvae and the chrys- 
alids, which have passed the winter in 
cold rooms outside the hives. Still from 
the natural surroundings of these insects 
we may easily believe that they have 
developed a constitution more susceptible 
to the cold than insects whose habits 
bring more exposure. 
Mr. W. H. Edwards has shown how 
the development of butterflies may be 
retarded by the cold. The bearing of 
these experiments upon the formation of 
different broods of a species and charac- 
teristic markings of each brood is of very 
great interest. 
Among honey bees of the genus Apis, 
we note peculiarities in respect to cold, 
which, like their habits and instincts, 
seem to separate them widely from most 
other insects, and strongly remind us of 
the vertebrates. Most insects freeze up 
in winter, so that all their functional ac- 
tivities are held in abeyance, ready to 
start into action at the touch of revivify- 
ing warmth, which ever comes with 
returning spring. A few of the higher 
ones really hibernate. There is slight 
activity of the tissues which is sustained 
