SOME AQUATIC INSECTS 93 



of the very abundant secretion of its salivary 

 glands, the Chironomous larva weaves together 

 particles of earth and leaves so as to form a kind 

 of burrow in which it rests with its head project- 

 ing when feeding; or with the tail-end of its 

 body projecting and waving to and fro in the 

 water, apparently as a help to respiration, which 

 is probably effected through the thin walls of the 

 long flexible tubes attached to the last segment 

 of the body. On account of the great transpar- 

 ency of its body, a young living Chironomous 

 larva is a most interesting creature to examine 

 under the microscope, as its internal organs can 

 be quite clearly seen, and their functions easily 

 observed. It is a wonderful sight to witness the 

 heart of the larva at work. It is a transparent 

 tube, on the dorsal surface and at the hinder end 

 of the body, and the rhythmic contraction of its 

 muscular walls driving the blood along the 

 narrow dorsal vessel, which passes above the 

 alimentary canal to the head, can be clearly fol- 

 lowed. The nymph is readily recognized by the 

 almost bushy tufts of respiratory filaments which 

 project from the front of the thorax, and which 

 replace the respiratory trumpets peculiar to the 

 nymphs of most aquatic Diptera. The perfect 

 insect is frequently to be observed in a very 

 characteristic position, with its fore-legs raised, 

 resting upon a window-pane. The antennae of 

 the male are large, bushy, and somewhat cone- 

 shaped ; while those of the female are smaller 

 and simple in character. 



Probably the quaintest in appearance of all 

 aquatic larvae are the Caddis-worms, who are 



