The Midges 



work on Chironomus by the above mentioned authors. The 

 larvae are found in gelatinous tubes attached to stones in slow 

 or swift-running streams. When disturbed they leave their cases 

 and crawl like measuring worms or swim with a figure-of-eight 

 motion. The larva is pale green in color and about seven mm. 

 long and has no anal blood-gills. When about to pupate the 

 thorax is much swollen. The pupae live in gelatinous cases 

 attached to stones, each case having a slightly protruded orifice 

 at either end so that the water flows through impelled by the 

 motion of the body of the pupa. The pupa breathes by means 

 of respiratory trumpets which are so small as to suggest that the 

 insect also breathes cutaneously or in some other way. It is 

 armed with strong hooks on the abdominal segments by means 

 of which, when mature, it tears its way through the case and rises 

 to the surface of the water. In this position the skin of the 

 thorax cracks and the adult fly emerges. 



112 



