Hi THE PHILOSOPHY 



But Nature, in this laft ftage of their exiflence, has not left them 

 without proper refources for the introduction of air into their bo- 

 dies. Inftead of protuberant tracheae in the form of tails or horns, 

 they now, like other flies, receive air by means of ftigmata, or 

 holes, varioufly difpofed over different paits of the body. 



The nymph of the libella, or dragon-fly, refpires water, in the 

 fanse manner as men and quadrupeds refpire air. We receive and 

 throw out the air by the mouth and noftrils. But the nymphs of 

 the libella receive and ejeft water by an aperture at the termina- 

 tion of their bodies. Thefe nymphs fometimes throw out the wa- 

 ter, at certain intervals, with fuch force, that the ftream is percep- 

 tible at the diftance of two or three inches from their bodies. When 

 kept fome time out of the water, the defire or necefTity of refpira- 

 tion is augmented ; and, accordingly, when replaced in a vefl^el 

 filled with water, infpirations and refplrations are repeated with un- 

 ufual force and frequency. If you hold one of thefe nymphs in 

 your hand, and apply drops of water to the pofterior end of its bo- 

 dy, it inftantly, by an apparatus fimilar to the pifton of a pump, 

 fucks in the water, and the dimenfions of its body are vifibly aug- 

 mented. This water is again quickly thrown out by the fame in- 

 ftrument. But, though this infeiSl: refpires water, air feems to be 

 not the lefs neceflfary to its exiftence ; for, like other infeds, the 

 whole interior part of its body is amply provided with large and 

 convoluted tracheae ; and, externally, there are feveral ftigmata def- 

 tined for the introdudion of air *. 



The worms, or nymphs, of the ephemeron flics merit attentiom 

 They have received the denomination of ephemeron, becaufe almoft 

 none of them furvive the day in which they are transformed into 



flies. 



* Reaumur, torn. 12. pag. 187. iz" edit. 



