220 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



searches of Dutrochet, Dubost, Newport, and others. The 

 observations in question were made by Mr. Maurice Girard, 

 with both the thermo-electric pile and the mercurial ther- 

 mometer. From an abstract of the results obtained we learn 

 that in the larva? and pupae of insects with a complete -meta- 

 morphosis, especially caterpillars with smooth bodies, the 

 temperature of the surface descends below that of the sur- 

 rounding air, showing that the evolution of heat by the res- 

 piratory combustion may be insufficient to compensate for 

 the loss due to the superficial evaporation or cutaneous trans- 

 piration. In the case of chrysalids, the cocoon, in which the 

 pupae of many lepidoptera and hymenoptera envelop them- 

 selves, seems specially intended, among other objects,, to pre- 

 vent too rapid a drying of the animal, such as would induce 

 a fatal superficial refrigeration. Indeed, at the moment of 

 being taken out of the cocoon, pupa? usually present a distinct 

 elevation of temperature, but, exposed to the air, they lose 

 weight by evaporation, and the surface temperature of their 

 bodies often descends below that of the surrounding air. 

 When the temperature approaches nearly to 32 Fahr., a su- 

 perficial cooling, due to evaporation, does not appear to be 

 produced. 



Adult insects, even when sleeping or very weak, always 

 have their temperature either equal to or slightly above that 

 of the air. The larva? and pupae of insects with incomplete 

 metamorphosis resemble adults in this respect. Mr. Girard 

 also ascertained that the temperature varies appreciably in 

 different regions of the body, especially in insects with pow- 

 erful aerial locomotion, where the difference in heat between 

 the thorax and abdomen in this respect may be very consid- 

 erable. In the bumble-bees and in the sphingidae the excess 

 of the thoracic over the abdominal temperature sometimes 

 amounts to from 1 to 18 Fahr., the heat in the flying insect 

 being concentrated in the thorax with an intensity propor- 

 tioned to the power of flight. This appears to result from 

 the fact that in the thorax are situated the strong muscles 

 both of the legs and wings, which in energetic contraction 

 during flight become the seat of an active combustion. 



Again, in the bumble-bees and some other insects the ex- 

 ternal evolution of heat was found to be in relation to the 

 buzzing, the temperature falling as soon as the buzzing ceases, 



