'Si'HE FLT. 53^' 



tey the body, you find it provided with ther organs of 

 refpiration. Four fmall fligmata, for this purpofe, are 

 found upon the thorax, and a greater number difperfed 

 over the annuli of the abdomen. The covering of the 

 different parts of the abdomen are fcalj, and do not con- 

 fift all of one piece, but admit of the contraction and di- 

 ' latation of that part, according to the circumfiances of 

 the animal. Each of the feet terminates in a fiiiail bunci* 

 oifetce, refembling a brufh. 



The interior organization of this genus, when examin- 

 ed with a proper apparatus, prefents two pulmonary facs 

 of a white colour, arranged longitudinally along the body. 

 As the bodies of fome fpecies are diaphanous, the adliora 

 of the heart may alfo be difcerned, as well as the liquor 

 it contains, continuilly driven along the great artery 

 leading to it, and returning by the fame courfe*. During 

 their larva ilate, the flies in general go through a greater 

 variety of metamorphofes than even the iilk or butterfly 

 worms : During their progrefs from the vermicular ta' 

 the chryfalis ftate, they pafs through an intermediate 

 change, unexperienced by other infe£ls. From the Ihort* 

 nefs of their lives, all thefe viciffitudes muH rapidly fuc- 

 ceed each other : this circumftance, however, dues not 

 prevent many fpecies from conflrudling a*coque for their 

 lafl: metamorphofis, of a curious fabric. The greater 

 part of thefe coques are of Iilk, with a mixture of other 

 materials ; thofe, indeed, mod common with us, ferve 

 themfelves with their own flcin, which becomes an in- 

 Cruftated covering to prote6l them during their dormant 

 and aurelia (late. 



Whes 



• Idem, ubi fuprsi 



