FIELD BOOK OF PONDS AND STREAMS 



flattened and sprawling and there is a tuft of white hairlike 

 gills at the base of each of the lateral appendages on the first 

 seven abdominal segments. Corydalis larvae avoid the light 

 and are seldom seen unless stones are suddenly pulled from 

 the rapids; then they cling to the surface or hitch themselves 

 rapidly backward by their posterior grappling hooks. In May 

 and June when they are about three years old they crawl out 

 on shore and under a stone or log to pupate. At first the 

 pupa is pale-colored and soft but it gradually darkens during 

 the pupal life which lasts about ten days. 



The adults have cinnamon brown bodies, and gray-white 

 spotted wings which measure four or five inches from tip to 

 tip when fully expanded. The female (Fig. 185, 3) has short, 

 stubby mandibles but those of the male (Fig. 185, 2) are 

 tusklike, more than three times the length of the head, and 

 used to hold the female during mating. As adults the dobson- 

 fiies are short-lived, and although they have strong jaws 

 they probably eat nothing. They are often attracted to 

 lights at night and sometimes fly high about street lamps, 

 usually falling to the ground after a few circles. The eggs 

 are laid on stones or sticks overhanging the water and there 

 may be two thousand or more of them in a single chalky 

 white mass but an inch wide. 



Fish-flies, Chauliodes pectinicomis. — The larvae of Chau- 

 liodes (Fig. 186, i) are similar to Corydalis but do not have 

 gill tufts at the bases of the lateral filaments and when full- 

 grown they are only half as large. They are not confined to 

 swift streams, but are often found clinging to submerged 

 trash in quiet side waters. They are predacious, those kept 

 in aquaria being successfully fed upon live backswimmers 

 and house flies. The length of the larval life must be con- 

 siderable, for Davis kept them in running water from Septem- 

 ber 1899 to June 1900 yet even at that date they had not 

 completed their growth. Like Sialis and Corydalis they 

 pupate beneath stones on the stream banks. 



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