560 HYBERNATION OF INSECTS. 



of a contrary description recorded by Reaumur and corroborated by the 

 ahiiost universal sentiment of writers on bees. After all, however, on 

 this point, as well as on many others connected with the winter economy 

 of these endlessly-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 sufhcient 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 t+iis 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 

 pupa; 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 

 infinitely thinner than that of hens' eggs, which John Hunter found to 

 freeze at about 15° of Fahrenheit. Yet on exposing several of the for- 

 mer, mcluding 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 



' 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 Transactions, " On the 

 Temperature of Insects," has come to the conclusion that Huber is altogether in error in 

 assigning a heat of 86° or SS° Fahr. to a populous hive, which, he contends, has its tempe- 

 rature 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 atmos- 

 phere, or about 52'= (Table XVl. 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 temperature of an adjoining hive was only 48 = -5 (p. 304.) ; and it is 

 from this circumstance that he supposes Ruber's error to have arisen, as the mere excite- 

 ment caused by introducing 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 hybernaling sleep, liable to constant interruption by 

 considerable external vaiiations of temperature or accidental excitement (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 seems 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 results of Mr. Newport's own observations show that bees preserve their activity, 

 and even leave the hive nnd collect pollen, when the external temperature is 40°-38, and 

 that of the hive only 47^-28 (Table XVI. Nov. 6), and they may, consequently, 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 obser- 

 vations, the interior of their hives often descends in our winters. 



