The Caddis Flies 



The caddis flies are often seen about the margins of streams 

 and frequent shady places. They seldom fly during the day, 

 but are often attracted to light at night. 



The eggs are laid in a double mass, which is gelatinous, and 

 usually green in color. This mass is usually attached to the 

 surface of some water-plant, but it is supposed that certain 

 species creep down the stems of aquatic plants under water for 

 the purpose of laying their ejzgs. The larvae are all aquatic, with 

 the exception of one form, which lives in damp moss on land, 

 and they are nearly all protected by a case of some form or 

 another. The cases, as just stated, may be composed of leaves, 

 either attached by their edges or placed longitudinally, or they 

 may be bits of stick arranged in many different ways, or stones, 

 or grains of sand, or even water-snail shells may be used for the 

 purpose, attached to the outside of the case, in such cases sand 

 being the main material. All of these different substances are 

 fastened together by means of silk, spun by the larvse, and they 

 serve to protect the caddis worms from the predatory insects so 

 often found in streams, and also from fish as well. 



In the majority of instances the cases are cylindrical, but 

 sometimes they are curved in a horn-like manner, and in other 

 cases they are very strangely involuted, like a snail-shell. In 

 fact, the case of a caddis worm was once described by a con- 

 chologist as a new species of snail-shell. Then there is another 

 form in which the case resembles a bottle with the bottom cut 

 away and the lower part compressed until only a slit is visible. 

 In the majority of instances the cases are free, and the larva 

 crawls or swims about with only its head and thorax protruding 

 from the orifice, but in other instances they are firmly attached 

 to rocks or submerged logs. 



The larva itself is elongate and usually cylindrical, and while 

 the head and thorax are tough and horny, the abdomen is thin- 

 skinned, delicate, and of a pale color. It breathes by means of 

 tracheal gills, which issue from the sides of the abdomen. It is 

 not known how many times any of them shed the skin and 

 a molt has never been observed to my knowledge. They live 

 several months in the larval stage, and most of them pass the 

 winter in that condition. When ready to transform to pupa, 

 both ends of the case or tube are protected by a silk netting, 

 spun by the larva, which transforms in security, well drawn back 



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