Microscopical Essays. 251 



fexes in other clafles till they have moulted, or put off their laft 

 fkin, the cancri and monoculi excepted. 



Mr. de Reaumur mentions fix or feven fpecies of two-winged 

 flies that are viviparous, bringing forth worms, which are after- 

 wards transformed into flies. The womb of one of thefe is 

 Jingularly curious : it is formed of a band rolled up in a fpiral 

 form, and about two inches and a half in length ; fo that it is feven 

 or eight times longer than the body of the fly, and compofed of 

 worms placed one on the fide of the other with wonderous art : 

 they are many thoufands in number.* 



The habits of the pucerons are fo very Angular, that I cannot 

 pafs them over in filence ; the more fo, as they are a very curious 

 objecl: for the microfcope. They are called by various names, 

 the proper one is aphis ; that which they are moft known by is 

 puceron, though they are fometimes called vine fretters and 

 plant lice. They belong to the hemiptera order. The roftrum 

 is inflecled, the antennae are longer than the thorax, fome have 

 four erecl wings, others have none at all : towards the end of the 

 belly there are two tubes, from which is ejecled that moil delicate 

 juice called honey-dew. 



The aphides are a very numerous genus ; Linnaeus has enume- 

 rated thirty-three different fpecies, whofe trivial names are taken 

 from the plant which they inhabit, though it is probable the 

 number is much larger, as the fame plant is often found to fup- 

 port two or three different forts of aphides. 



H h 2 An 



* Reaumur Mem. des Xnfe&es, torn. 4, p. 415. 



