FIELD BOOK OF PONDS AND STREAMS 



Fig. 187. — Spongilla-fly, Sisyra umhrata, which 

 lives in fresh water sponges: i, lar\^a; 2, adult. 



Their pale-colored larvse (Fig. 187) live in the cavities of 

 a fresh water sponge and feed upon its substance (p. 109) 

 Their bodies are sparsely covered with bristles which catch 

 torn fragments of the sponge and effectually camouflage them. 

 Their long, slender jaws are grooved on the inner sides so 

 that when they are held together they form a tube. This is 

 thrust into the soft sponge and its tissues are sucked up 

 through it. Either the food thus secured contains little 

 waste or it is wholly absorbed in the stomach, for there is no 

 posterior opening to the alimentary canal and it is unlikely 

 that waste could pass out at the mouth as it does in Hydra. 

 The fullgrown larva finally leaves the sponge, climbs out of 

 water to some leaf or twig and spins its silken pupal cocoon. 

 This silk is produced by its kidne\"-like Malpighian tubules 

 which have taken on a silk-secreting function. It comes out 

 of the hind end of the body through spinnerets similar to 

 those of spiders. 



There are two genera of Spongilla-fiies which have similar 

 life-histories and make such cocoons. Larvce of Climacia 

 weave a cocoon covered with a hexagonal meshed net while 

 Sisyra makes one covered with a sheet of silk. Lengt.i of 

 Sisyra larva, about one quarter inch. 



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