146 



HALF HOUES WITH ENSECTS. [Packard. 



Of those insects whicb extract air from the water in which 

 they live and are not obliged to ascend to the surface, is the 

 young of the plumed gnat (Fig. 110, CJdronomus oceanicus^ 

 male, and beneath, head of female ; a, larva and head en- 

 larged). These worms are very abundant in every mud 

 puddle, but the species here figured lives at all depths in 



Fig. 110. 



Ocean Gnat; a, larva, and head enlarged. 



the sea down to over a hundred feet. Some larvte of an- 

 other species were dredged in Lake Superior by Mr. S. I. 

 Smith at a depth of one hundred and fifty-five feet. They are 

 usually provided with two pairs of fleshy filaments, perme- 

 ated by one or two slender tracheal twigs, connecting with 

 a slender pair of tracheae running through the body, and 



18 



