LUCY WRIGHT SMITH 
433 
STUDIES OF NORTH AMERICAN PLECOPTERA (PTERO- 
NARCINAE AND PERLODINI) 
BY LUCY WRIGHT SMITH 
Introduction 
Plecoptera, or stone-flies, are of universal distribution; they 
are found on all the continents and in all climates from the 
arctic region to the tropics. For the most part the adults are 
dark brown, inconspicuous insects with elongate, depressed 
bodies, long, slender antennae and setae, and two pairs of mem- 
branous wings which lie folded over the body in a horizontal 
position when the insects are at rest. In general, stone-flies are 
poor fliers and can be found crawling around the stones, on banks 
of streams or on nearby trees much oftener than on the wing. 
Ordinarily they are not seen in great numbers on account of their 
more or less protective coloration and their habit of crawling 
away into hiding in cracks and crevices. The immature form, 
the nymphs, are found much more abundantly. These can be 
seen in almost any stream, on the under side of stones, or hidden 
away in masses of drifted leaves. Aside from the absence of 
wings, they are much like the adults in form. The majority of 
them possess tracheal gills, situated usually on the ventral side 
of the thorax, but they may occur on the under side of the head, 
on the basal abdominal segments, or at the tip of the abdomen. 
Despite the wide distribution of stone-flies and their compara- 
tive abundance, .a large collection of them is rarely found in the 
possession of institutions or individuals. Likewise, the amount 
of work, that has been done on the order, is very small. A few 
systematists have been interested in them and have described a 
good many, but aside from that the}^ are little known. Only 
occasionally has some biological or morphological aspect of a 
genus or species attracted anyone’s attention. 
My own interest in the group is primarily ecological, and my 
first two years’ study of it was of that nature. During that time 
many life-histories were obtained, and considerable interesting 
data were accumulated on such things as emergence, feeding 
TRANS. AM. ENT. SOC. XLIII. 
