The Dobson and its Family- 



breathing filaments situated just beneath each side of the 

 abdomen. They also, when they approach full growth, have 

 spiracles, which are closed, however, until the creature is ready 

 to emerge from the water. The number of molts is not recorded. 

 When full grown (two years and eleven months after its birth), 

 the larva leaves the water, and crawls about seeking a suitable 

 place for pupation. It does not travel very far, but it crawls 

 energetically while it is about it, curiously enough, climbing trees 

 occasionally, and on several occasions in Illinois they fell down 

 the chimney of a house occupied by the man who kept the toll 

 bridge over the Rock River. They travel on land only by night, 

 hiding under some stone or log during the day, and it is under 

 stones and logs that they finally pupate. 



The larva in color is dark slate-gray, and is remarkably 

 thick-skinned and tough. This fact adds to their value as bait, 

 since one will last a long while. The pupa, however, is light 

 yellow in color, and transforms to the adult fly in about a month. 

 Full grown larvae begin to emerge from the water in May, and 

 the adults are seen flying a month later. 



In rapid, rock-bottomed streams, where these insects abound, 

 the method of catching them is to wade in the streams with a 

 net and lift up the stones in advance, catching the larvae in the net 

 as they float down with the current. 



They bear at the sides of the body, in addition to the respira- 

 tory tufts mentioned above, two long filaments on each side, 

 which are furnished with hairs, and may be of some service in 

 swimming. Possibly, also, with the very young larvae they have 

 a respiratory function. When the larvae become large, however, 

 dissection shows that the tracheae contained in these filaments are 

 insignificant, whereas each element of the branchial tufts 

 possesses a strong branched trachea. 



Mr. R. S. Clifton has found an interesting little dark-colored 

 beetle (Anihicus haldemanni) along the Potomac River, feeding 

 upon the egg masses of the hellgrammite fly. The beetle was 

 found to lay its eggs upon the egg masses and its larvae were 

 found destroying the eggs. Sometimes as many as a dozen of 

 the larvae were found in a single egg mass. 



215 



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