NEUROPTERA 



287 



presence of a pair of anal prolegs, each of which bears a pair of hooks. 

 Six species are found in the United States and Canada; these repre- 

 sent four genera, which can be separated as follows. 

 A. Latero-caudal angles of the head with a sharp tooth. Large insects, p. 287 



CORYDALUS 



AA. Latero-caudal angles of the head unarmed. Insects moderately large; the 

 fish-flies. 

 B. Wings somewhat ashy in color with more or less dusky markings. 



C. Veins of fore wings marked with dark and light, uniformly alternate. 



p. 288 Chauliodes 



CC. Veins of fore wings uniform in color except where dusky markings 



cross them,, p. 288 Neohermes 



BB. Wings black or brown with white markings, p. 288 Nigronia 



Corydalus. — The only member of this genus in our fauna is 

 Corydalus cornutus. This is a magnificent insect, which has a wing- 

 expanse of from 100 to 130 mm. Figure 321 represents the male, 



JcfA 2d A Cui Cuia 



Fig. 320. — Fore wing of a pupa of Corydalus. 



which has remarkably long mandibles. The female resembles the 

 male, except that the mandibles are comparatively short. 



The larvce are called dob sons or hellgrammites by anglers and 

 are used by them for bait, especially for bass. Figure 322 represents 

 a full-grown dobson, natural size. These larvas live tmder stones in 

 the beds of streams. They are most abimdant where the water flows 

 swiftest. They feed upon the naiads of stone-flies and May-flies and 

 on other insects. 



The larvae of Corydalus dift'er from those of the following genera 

 in the possession of a tuft of hair-like tracheal gills at the base of 

 each of the lateral appendages on the first seven abdominal segments. 



When about two years and eleven months old, the larva leaves 

 the water and makes a cell under a stone or some other object on 

 or near the bank of the stream. This occurs during the early part 

 of the summer ; here the larva changes to a pupa. In about a month 

 after the larva leaves the water, the adult insect appears. The eggs 

 are then soon laid; these are attached to stones or other objects 

 overhanging the water. They are laid in blotch-like masses, which 

 are chalky white in color and measure from 1 2 mm. to nearly 25 mm. 

 in diameter. A single mass contains from two thousand to three 

 thousand eggs. When the larvae hatch they at once find their way 

 into the water, where they remain imtil full-grown. 



