1 90 Royal Society. 



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 prose- 

 cution 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 indi- 

 vidual 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 

 ensuring 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 compa- 

 rative 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 tem- 

 perature. 



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 ap- 

 pears that those which possess the highest temperature are always 

 volant insects, and are chiefly diurnal species, residing almost con- 

 stantly 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 tempera- 

 ture above that of its surrounding medium, is in the larva from o, 9 

 to 1°5 ; while in the imago it is from 5° to 10°. Among the hymeno- 

 ptera it is from 2° to 4° in the larva, and in the imago from 4° to 15° 

 or even 20° j 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 hyberna- 

 tion, which he ascribes, in every state of the insect, to accumu- 

 lations 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 materials has been exhausted. A variety 

 of experiments are related, tending to prove that a large proportion 

 of the heat evolved by an insect, when in a state of great activity, 

 is dissipated into the surrounding medium, and that the quantity of 



