INTERNAL ANATOMY OF INSECTS. 35 



speedily perish in air altogether deprived of its oxygen, 

 or placed in situations to which all access to this essential 

 element is excluded. Their respiration too of atmo- 

 spheric air produces the same change in it with that of 

 the vertebrate animals, the oxygen disappearing, and 

 carbonic acid gas being produced in its place. Boyle 

 had long since ascertained, that when bees, flies, and 

 other insects were placed under an exhausted receiver, 

 they often perished a : and the same effect was even ob- 

 served by the ancients to ensue, when their bodies were 

 by any means covered with oil or grease, which necessa- 

 rily closed the orifices of their respiratory organs b . 



But for the first series of experiments ascertaining the 

 necessity of a supply of air to insects, and their conver- 

 sion of it into carbonic acid, we are indebted to the illus- 

 trious Scheele c ; and his experiments have been repeated 

 and confirmed by Spallanzani, Vauquelin, and other che- 

 mists. The former found, that when caterpillars and 

 maggots were confined in vessels containing only about 

 eleven cubic inches of atmospheric air, though furnished 

 with sufficient food, they soon died, and sooner when the 

 space was more confined d . He ascertained too, that a 

 larva weighing only a few grains consumed, in a given 

 time, as much oxygen as an amphibious animal a thou- 

 sand times as voluminous e . A male grasshopper (Acrida 

 viridissima) in six cubic inches of oxygen lived but 

 eighteen hours, and the female placed in eight cubic 

 inches of atmospheric air, only thirty-six hours. The 



a Pkilos. Trans, v. 2011. Works, 4to. i. 79, 112. 



b Aristot. Hist. Animal. I. viii. c. 27. 



c On Air and Fire, 148, 155. d Tracts, 208. 



e Mem. on Respirat. 75. 



D 2 



