156 M. Dutrochet on the 



an indisputable fact, that insects have a temperature, although 

 little higher than that of the surrounding medium."'' * 



According to Mr Newport, the vital heat of insects is 

 greater in the perfect state than in the larvae ; higher in a 

 state of excitement than of repose ; higher when the insect is 

 awake than when it sleeps ; it is diminished by want of food, 

 and increases with the frequency of the pulsations of the dor- 

 sal vessel, and with the activity of respiration. Mr Newport 

 thinks that, by augmenting at pleasure the activity of respira- 

 tion, insects can by that means voluntarily increase the degree 

 of their vital heat. 



I have been unable to repeat all Mr Newport's experiments. 

 The mode of experimentation employed by me necessarily 

 threw the insects I was observing into a state of excitement ; 

 they were either fixed immoveably to the spot, or in a state 

 of agitation, although retained in a particular place, I refer 

 to my memoir for an explanation of my method of proceeding; 

 I limit myself here to a comparison of the results at which I 

 arrive with those of Mr Newport. I have reduced the degree 

 of Fahrenheit's thermometer, which the English observer made 

 use of, to centesimal degrees: I cannot notice all his experi- 

 ments, for they are very numerous. 



Mr Newport found in the Bombus terrestris a vital heat of 

 from 0'.99 F. to 1)°.36 F. (0°.55 to 5°.2 C), according as it was 

 in a state of rest or excitement. In my experiments, the heat 

 of this insect was not raised above 0.45 of a degree of F. (a 

 quarter of a centesimal degree). I found the same vital heat 

 in Bombus lapidarius,, Bomhus hortorum^ and Xyhcopa molacea. 



The larva of the common cockchaffer (Alelolontha valoris) 

 afforded to Mr Newport a heat of 0.59 of a degree of Fahren- 

 heit, or 0.33 of a centesimal degree ; in my experiments it did 

 not exceed 0.04 of a centesimal degree, equal to 0°.07 F. The 

 cockchaffer, in its perfect state, having the ball of the thermo- 

 meter sunk in its abdomen, was found by Mr Newport to have 

 a vital heat of 2°.79 F. to 4°.68 F. (1°.55 to 2°.6 Cent.). I never 

 saw it exceed 0.32 of a degree of F., or 0,18 of a centesimal 

 degree, the insect being in an immoveable state. When in a 

 state of agitation, Mr Newport found that the cockchaffer had 

 a heat of 9° F. (5° Cent.) above that of the surrounding air ; 



* Annales de Physique et de Chiniie, t. 48, p. 207. 



