NEUROPTERA. 



221 



more than half as long as the rest of the body. This species is 

 common throughout the greater part of the United Stale-. The 

 larvae are called " Dobsons" by anglers, and are used by them for 

 bait, especially for bass. Fig. 191 represents a fully grown Dob- 

 son, natural size. There is on each abdominal segment a pair of 

 long tapering appendages ; those of the ninth 

 abdominal segment are carried back so as to 

 project from the sides of a pair of anal pro- 

 legs. These pro-legs project caudad, and are 

 furnished each with a pair of claws. At the 

 base of each lateral appendage on the first 

 seven abdominal segments there is a tuft of 

 hair-like tracheal gills. The larva also has 

 spiracles; a remarkable instance of an insect 

 provided with both organs for aquatic and 

 aerial respiration. The spiracles are probably 

 not used till the insect is fully grown and 

 leaves the water to undergo its transforma- 

 tions. These larvae live under stones in the 

 bed of streams. They are most abundant in 

 the swifter parts of the stream. The}- are 

 carnivorous, feeding upon the larvae of Stone- 

 flies, May-flies, and other insects. When 

 about two years and eleven months old, the 

 larva leaves the water and makes a cell under 

 a stone or other object on or near the 

 bank of the stream. This occurs at Ithaca during the latter part 

 of May or early in June. By the middle of June the majority of 

 these larvae have transformed to pupae. These are of a yellowish- 

 white color. The\- are furnished with rudimentary wings and legs. 

 and quite long antennae. During the last half of June the pupae 

 change to the adult .-rate. The eggs are soon laid. These are- 

 attached to stones or to other objects overhanging the water. 

 They are laid in blotch-like masses, which are chalky white in color 

 and measure from 12 to 20 mm. in diameter. A single mass con- 

 tains from two thousand to three thousand eggs. When the larvae 

 hatch they at once find their way into the water, where they remain 

 till full}- grown. 



Rapliidia. — This genus is represented in this country only on the 

 Pacific Coast. It is distinguished from the other members of the 

 family by having the prothorax cylindrical, and in having the wings 

 15 



Fig. ioi. — CorydalU cornu- 

 rva. 



