Microscopical Essays. 703 



divifions of the thorax ; the abdomen is divided into eight rings, 

 from the edges of each of which three or four briftles proceed. 

 The tail is divided into two parts, of very different forms ; by 

 one of thefe it can fteer itfelf any way, in the other we may dis- 

 cover two pulmonary tubes, through which the infe6l breathes. 

 The larva has a power of moiftening the tail with an oleaginous 

 liquor, by which means it can fufpend itfelf on the furface of the 

 water. On agitating the water, the worms defcend with precipe 

 tation to the bottom ; but they foon return to the furface, to 

 breathe the air through the tube that is annexed to their tail. 

 They pafs from this ftate into that of the pupa, which is the gnat 

 inclofed in a thin fkin, under which it is formed and ftrengthened, 

 the organs of refpiration are changed, breathing in this ftate 

 through a couple of horns, which are placed near the head, 

 keeping itfelf rolled upon the furface of the water, though on, 

 the leaft motion it defcends, unrolling itfelf, aided by the oars near, 

 ihe taiL 



From the fpoils of the pupa, a little winged infee! proceeds,, 

 whofe every part is afHve to the laft degree, and whole whole 

 ftrufture is thejuft objeft of our admiration. It's head, adorned 

 with feathers, is a fine microfcopic objea ; but the probofcis may 

 be deemed one of the molt curious inftruments in the infect cre- 

 ation. It confifts of a fealy (heath ; at about two-thirds from the 

 end of this there is an aperture, through which it darts four 

 pieces; one of thefe is, however, no more than the cafe in which, 

 the others lie concealed*. 5 



