The May-flies and Stone-flies 



7 1 



of the abdomen as in the May-fly nymphs. The feet of the stone-flies have 

 two claws, while those of the young May-flies have but one. The stone-fly 

 nymph has a pair of large compound eyes, as well as three small simple eyes, 

 strong jaws for biting and chewing (perhaps for 

 chewing heir nearest neighbors, the soft-bodied, 

 smaller May-fly nymphs!), and two slender back- 

 ward-projecting processes on the tip of the abdomen. 

 The legs are usually fringed with hairs, which makes 

 them good swimming as well as running organs. 

 The nymphs can run swiftly, and quickly conceal 

 themselves when disturbed. 



All stone-fly nymphs, as far as known, require 

 well aerated water; they cannot live in stagnant 

 pools or foul streams. Needham says that a large 

 number of the smaller species are wholly destitute 

 of gills absorbing the air directly through the skin. 



Nymphs brought in from a brook and placed in a FIG. 106. Young(nymph) 



, ,. .,. , -.11 rn j of stone-fly, from Cah- 



vessel of still water will be seen with claws affixed, fornia. (Twice natural 



vigorously swinging the body up and down, trying size -) 

 to get a breath under the difficult conditions into which they have been 

 brought. The food-habits are not at all well known: some entomologists 

 assert that small May-fly nymphs and other soft-bodied aquatic creatures 

 are eaten, while others say that the food consists of decaying organic matter. 

 Here is another opportunity for some exact observation 

 by the interested amateur. On the other hand it is per- 

 fectly certain that the nymphs themselves serve as food 

 for fishes. 



The fully worked-out life-history of no stone-fly seems 

 to have been recorded. The eggs, of which 5000 or 6000 

 may be deposited by a single female, are probably dropped 

 on the surface of the water, and sink to the bottom 

 after being, however, well distributed by the swift current. 

 Sometimes the eggs are carried about for a while by the 

 female, enclosed in a capsule attached to the abdomen. 

 The young moult several times in their growth, but 

 -Exuvia P ro k a kly not near ly as many times as is common among 

 of nymph of stone- May-flies. When ready for the final moulting, the nymph 

 fly. (Natural size.) craw l s ou t on a rock or on a tree-root or trunk on the 

 bank, and splitting its cuticle along the back, issues as a winged adult. 

 The cast exuviae (Fig. 107) are common objects along swift brooks. 



The adults (Fig. 108) vary much in size and color, the smallest being 

 less than one-fifth of an inch long, while the largest reach a length of two 



FIG. 107. ] 



