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- Fig. 103 .—Pteronarcys regalis. 
fly, Acroneura. 
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. 
