226 



Aquatic Organisms 



Midge larvae live mainly in tubes which they fashion 

 out of bits of sediment held together by means of the 

 secretion of their own silk glands. These tubes are 

 built up out of the mud in the pond bottom as shown in 

 the accompanying figure, or constructed in the crevices 



^ ' ?T 



Fig. 134. Tubes of midge larvae in the bed of a pool. 



between leaves, or attached to stems or stones or any 

 solid support. They are never portable cases. They 

 are generally rather soft and flocculent. The pupal 

 stage is usually passed within the same tubes and the 

 pupa is equipped with respiratory horns or tufts of 

 various sorts for getting its air supply. The pupa (see 

 fig. 171 on p. 279) is active and its body is constantly 

 undulating, as in the caddisflies. 



The eggs of the midges are laid in gelatinous strings 

 ig plumps and are usually deposited at the surface of 

 the water. Figure 135 shows the appearance of a bit 

 of such an egg-mass. This one measured bushels in 



