PLECOPTERA NYMPHS OF NORTH AMERICA 27 
Biological Notes 
The nymphs of this family are all herbivorous and feed upon 
almost any kind of fresh and decaying vegetable matter. Stomach 
examinations often reveal large pieces of wood and other vege- 
table matter in the intestines of the large nymphs. The nymphs 
are not adapted to live in swift running water and normally in- 
habit the small upland spring brooks which are not subject to 
disturbance by floods. Here in the accumulated debris on the 
bottom of the little streams one will find the nymphs well pro- 
tected by the concolorous brown of their bodies which simulate 
short pieces of dead and decaying wood. The nymphs are very 
clumsy and are unable to move rapidly. Upon being taken out of 
the water, they curl up, remain motionless for some time, and 
thereby easily escape detection in the debris. 
Smith (53) quotes Barnston as saying that ‘‘it [Pteronarcys 
nymph] constantly resided in the water at the bottom of streams 
and rivers,’’ and then states further, ‘‘I have always found it 
clinging to the under side of stones in the most rapid parts of 
streams.’’? Muttkowsky (21) reports Pteronarcys nymphs from 
rapid water streams in Yellowstone Park. I have found them very 
common only in the smaller spring brooks, and only occasionally 
have I observed the nymphs in the swifter water. The nymphs of 
this family lack the stream-line form of body and their food 
habits would not seem to permit their remaining under stones 
in the rapid part of streams. 
Not much is known about the life history of the species of 
this family. The life cycle occupies not less than two years, and, 
in the genus Pteronarcys, in all probability occupies three years. 
Emergence takes place during the summer months, and it is very 
easy to rear the species if fresh running water is available. 
Genus PIERONARCYS Newman 
This genus includes our largest stoneflies, the mature nymphs 
measuring up to fifty millimeters or slightly more, in length. 
The nymphs are of an almost uniform chocolate to blackish color, 
more cylindrical than any of the other large stoneflies, and are 
further easily recognized by their copious white gills which cover 
the entire ventral surface of the thorax, as well as the first two ab- 
dominal segments. 
Head rather small and much narrower than the prothorax 
which flares somewhat over the head; antennae long, slender, 
tapering, and made up of fifty-five to sixty, or more, segments; 
the three ocelli forming an equilateral triangle, the hind ocelli 
