94 



THE STUDY OF INSECTS. 



flat creatures from one-half inch or less to one and one half 

 inches in length. They cling so closely and are so nearly the 

 color of the stone that they look almost like fossils. Their 

 antennae and caudal bristles and three legs on each side 

 extend out like the rays of a star ; the six soft clumps of 

 white hair-like gills, one behind each leg, alone show that 

 they are not engraved upon the stone (Fig. 102). These 

 insects are the nymphs of the stone-flies, and are the favorite 

 food of fishes, especially of brook trout. If a nymph is 

 fortunate enough to escape the fate of being a luncheon for 

 fish, when it is full-grown it crawls forth from the water and 



Fig. 102. — Nymph of Stone- 

 fly, Acroneura. 



Fig. 103. — Ptcronarcys regalis. 



transforms to a gray or greenish fly, with slender, closely 

 veined fore wings and wide, delicate hind wings (Fig. 103). 

 The cast nymph-skins are common objects on the banks of 

 the streams which these insects inhabit. Several of the 

 smaller species of the stone-flies appear in the winged state 

 upon snow in early spring, and often find their way into 

 houses. 



