II 



FLIES WITH AQUATIC LARV.^ 



121 



a flat, gelatinous sheet, in which the eggs are arranged 

 in spiral lines. 



I will add a few words about another Gnat-like 

 Insect, with aquatic larva and pupa, which in its larval 

 state was described and figured long ago by De Geer, 

 and has since received the name of Mochlonyx. In 

 habitat, mode of feeding, &c., the earlier stages much 

 resemble those of Corethra. Both larva and pupa 

 are structurally as exactly intermediate between 

 Corethra and Culex as can well be imagined. Thus 



Fu;. 35. — Fly of Corethra plumicornis, male. 



the tracheal trunks (air-tubes) are large in the Culex 

 larva, reduced in Mochlonyx, and rudimentary in 

 Corethra. The air-vesicles of the Culex larva are 



