138 



" catch liold " and await tlieir prey farther down stream. In spite 

 of their vicious looking jaws these insects are not venomous. At 



the very worst they could do no more 

 than pinch the finger of the unwary 

 explorer. 



When the Dobson is full grown, it is 

 called a Hellgrammite fly or horned 

 Corydalis. It has lost none of its ugli- 

 ness, though it has gained two pairs of 

 thin brownish gray wings, and flies about 

 in the evening. It has been known to 

 create some consternation by flying in at 

 an open window. It is harmless and 

 short-lived in the adult stage. 



Upturned stones are likely to bring 

 to view other strangers. Ljiug close 

 against their wet surfaces one usually 

 finds young May-flies. (See Fig. 91.)'^ 

 These, like the young dragon-flies, are 

 called nymphs. 



When they are ready to leave the water 

 they make their way to the shore and 

 clinging to some convenient tree trunk 

 or building they shed their nymph skins. 

 I have seen trees and buildings on the 

 banks of the St. Lawrence Kiver liter- 

 ally covered with these cast skins. In 

 the early morning in June and July one 

 can watch the molting process, the unfolding of the gauzy wings 

 and the unsheathing of the long filaments. (See Fig. 92.) 



Do not believe that May-flies are harmful. They are sometimes 

 too numerous for comfort at summer resorts where myriads of them 

 swarm about the lights. But stories of their stinging and biting 

 are entirely without foundation. They are short-lived in the adult 

 stage. The name of the family to which they belong, EphemeridcB^ 



91. — May -fly nymph, three 

 times natural size. 



* Figures 91, 92 and 93 are adapted from Dr. R. Leuckart's Zoological charts. 



530 



