526 HYBERNATION OF INSECTS. 
wonderful insects, there is evidently much yet to be observed, and many 
doubts which can be satisfactorily dispelled only by new experiments, 1 
The degree of cold which most insects in their different states, while 
torpid, are able to endure with impunity is very various ; and the habits of 
the different species, as to the situation which they select to pass the 
winter, are regulated by their greater or less sensibility in this respect, 
Many insects, though able to sustain a degree of cold sufficient to induce 
torpidity, would be destroyed by the freezing temperature, to avoid which 
they penetrate into the earth or hide themselves under non-conducting 
substances ; and there can be little doubt that it is with this view that so 
many species while pupe are thus secured from cold by cocoons of silk or 
other materials. Yet a very great proportion of insects, in all their states, 
are necessarily subjected to an extreme degree of cold. Many eggs and 
pupe are exposed to the air without any covering ; and many, both larve 
and perfect insects, are sheltered too slightly to be secure from the frost. 
This they are able to resist, remaining unfrozen though exposed to the 
severest cold, or, which is still more surprising, are uninjured by its in- 
tensest action, recovering their vitality even after having been frozen into 
lumps of ice. 
The eggs of insects are filled with a fluid matter, included ina skin in- 
finitely thinner than that of hens’ egas, which John Hunter found to 
freeze at about 15° of Fahrenheit. Yet on exposing several of the former, 
including those of the silk-worm, for five hours to a freezing mixture which 
made Fahrenheit’s thermometer fall to 38° below zero, Spallanzani found 
that they were not frozen, nor their fertility in the slightest degree im- 
1 Mr. Newport from his numerous experiments on the temperature of the interior 
of bee-hives in winter, recorded in his valuable paper in the Philosophical Transac- 
tions, “ On the ‘Temperature of Insects,” has come to the conclusion that Huber is 
altogether in error in assigning a heat of 86° or 88° Fahr. to a populous hive, which, 
he contends, has its temperature sometimes (though rarely) lowerthan that of the 
freezing point (p. 303.), and in the winter months does not average more than from 
7 to 9 degrees above that of the atmosphere, or about 52° (Table XVI. p. 335.), 
though merely tapping on the outside of the hive, by exciting the bees, will, at any 
time, greatly increase the heat: in one instance (Feb. 2.) to 102°, when the tempera- 
ture of an adjoining hive was only 4895 (p. 804.); and it is from this circumstance 
that he supposes Huber’s error to have arisen, as the mere excitement caused by ia- 
troducing a thermometer is sufficient to raise the heat to the point (86° or 88°) 
which that observer mentions. Mr. Newport admits that hive-bees are never 
strictly torpid, but pass the winter in a state of hybernating sleep; liable to constant 
interruption by considerable external variations of temperature or accidental excite- 
ment (p. 300.).— Without entering on a discussion which would require much 
greater space than can here be given, it may be remarked that something more than 
thermometrical observations seem required, before the express assertions, as above 
quoted, of such careful observers as Swammerdam and Bonnet—that bees feed and 
tend their young even in the midst of winter, and those of Huber, that bees then cluster 
together, and keep themselves in motion in order to preserve their heat, that they do 
not cease to ventilate the hive, and, on an emergency, set themselves to work in the 
middle of January—can be put aside as wholly unfounded. It may be true that 
Huber was deceived as to the actual thermometrical heat of the interior of his hive; 
yet the result of Mr. Newport’s own observations shows that bees preserve their 
activity, and even leave the hive and collect pollen, when the externa temperature 
is 40°-38, and that of the hive only 47-28 (‘Table XVI, Nov 6,), and they may, con 
sequently, feed their brood, and attend to the usual interior occupations of the hive, 
at a temperature not lower than this, to which lower temperature it does not appear 
likely, from Mr, Newport’s observations, the interior of their hives often descends in 
our winters, 
