Nerve-winged Insects; Scorpion-flies; Caddis-flies 225 



Two species of Sialis occur in this country; they are called alder-flies, 

 or orl-flies. The smoky orl-fly, Sialis injumata, widely distributed over 

 this country, is a dusky brownish in- 

 sect about \ inch long, often seen, with 

 wings closely folded, sitting on sedge- 

 leaves near quiet waters. The larvae 

 (Fig. 309), according to Needham, live 

 in marshy places filled with aquatic 

 plants, on the borders of streams and 

 ponds. When full grown they are 

 about an inch long, and keep up an 

 undulating motion with the abdomen, 

 the long tail being intermittently lashed 

 up and down. When full grown the 



larva crawls out of the water and at FIG. 309. Larva (at right) and pupa (at 

 some little distance burrows into the 

 moist soil for a few inches or even a 

 foot or more. Here it forms an oval cell and pupates within it. Two or 

 three weeks after the adult fly issues. 



Of Chauliodes, the fish-flies (Fig. 310), eight North American species 

 are known. The adults are from i to 2^ inches long, and their wings 

 expand from z\ to 4 inches. The wings are grayish or brownish with whitish 

 spots or bands, and the antennae are curiously feathered or pectinate. The 



left) of an orl-fly, Sialis infumata. 

 (After Needham; twice natural size.) 



FIG. 310. The saw-horned fish-fly, Chauliodes serricornis, laying eggs. 

 (After a photograph from life by Needham; natural size.) 



larvae live in wet places at the edge of water or in water close to the surface. 

 According to Needham they are perhaps oftenest found clinging to the under 

 side of floating lo^gs or crawling beneath the loosened bark. They are 

 predaceous, feeding upon other aquatic insects. When ready to transform 

 they excavate a cell above the level of the water under a stone or log or layer 



