370 PROCEEDINGS OF SOCIETIES. 



temperature in individual insects had been ascertained by himself prior to these 

 observations ; the results of which observations, together with other facts 

 connected with the physiology of insects, he subsequently communicated to 

 Dr. M. Hall. 



Since the time when the author has been engaged in the prosecution of this 

 inquiry, some observations on the same subject have been published by Dr. 

 Berthold, of Gottingen, who expresses it as his opinion that insects ought not 

 to be regarded as cold-blooded animals, but who does not appear to have detected 

 the existence of a temperature higher than the surrounding medium in any in- 

 dividual insect. The author also notices the observations on this subject made 

 by Hansmann, Juch, Rengger, Dr. John Davy, and others, some of whom 

 have detected, while others have not observed, the existence of an increased 

 temperature in this class of animals. He then gives a detailed account of the 

 precautions to be taken for insuring accuracy in making observations of this 

 kind ; and remarks that greater reliance is to be placed on those made on the 

 external than on the internal temperature of the animal, seeing that comparative 

 results are all that can be obtained, and that the injury inflicted on the insect by 

 its mutilation very materially interferes with the correctness of the conclusions 

 as to the degree of internal temperature. 



After premising these introductory remarks, the author gives a detailed account 

 of his observations on the temperature of insects in their several states of larva, 

 pupa, and imago, from which it appears that those which possess the highest 

 temperature are always volant insects, and are chiefly diurnal species, residing 

 almost constantly in the open air. He shows that the larva has a lower tem- 

 perature than the imago, and that the energy of its respiration is also less, 

 regard being had to the activity of the insect, and to the size of its body. In 

 lepidopterous insects the average elevation of temperature above that of its sur- 

 rounding medium, is in the larva from 0° *9 to 1° *5 ; while in the imago it is 

 from 5° to 10°. Among the Hymenoptera it is from 2° to 4° in the larva, and 

 in the imago from 4° to 15° or even 20°; but in all cases the amount of this 

 elevation is shown to depend on the degree of activity, and the quantity of air 

 respired during a given period. The author then inquires into the influence of 

 various circumstances, such as inactivity, sleep, hybernation, and inordinate 

 excitement, on the temperature of insects, and shows that the evolution of heat 

 gradually diminishes in a degree corresponding to the length of time during 

 which the insect remains in a state of repose, but that it is immediately increased 

 as soon as the insect is roused into action. He adverts also to the remote cause 

 of hybernation, which he ascribes, in every state of the insect, to accumulations 

 of adipose matter, or of nutrient fluid, which, being stored up in the system, 

 induce a plethoric state, from which the animal is aroused when this store of 



