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. * 



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 pupae 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 

 pupae are exposed to the air without any covering ; and many, both larvae 

 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 in a skin in- 

 finitely thinner than that of hens' eggs, 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 ot 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) lower than 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 48-5 (p. 304.) ; and it is from this circumstance 

 that he supposes Huber's error to have arisen, as the mere excitement caused by in- 

 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 external temperature 

 is 40-38, and that of the hive only 47 0> 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. 



