Family PERLIDAE 
This family includes most of the more brightly or strikingly 
colored nymphs. They are all carnivorous. Head as wide or 
shghtly wider than pronotum; either two or three ocelli; epi- 
cranial suture distinct; clypeo-frontal suture absent; antennae 
long and slender. Pronotum much wider than long, variously 
marked. Meso- and metanotum with the wing pads either only 
slightly produced and indistinctly set off from the body, or the 
wing pads may be produced into long, distinct appendages. Gills 
either present or absent. When present they may be small and 
finger-like (Perlodes), and attached to the submentum or thorax, 
or the gills may be present as tufted branches on the thorax, 
and in some eases tufted gills are also found attached to the 
subanal lobes between the cerci. The cerci are long and slender 
and made up of many segments. The mouth parts are of the 
carnivorous type and therefore differ in structure from the mouth 
parts of the other families. 
The labrum is very short and wide and bears a distinct epi- 
pharynx which is very flexible and may be extended or retracted. 
The mandibles are quite narrow, and beyond the teeth there is a 
fringe of hairs, but no molar. The maxillae also differ in structure 
from the maxillae of other families. The lacinia terminates in a 
long sharp ineurved tooth, and in most cases possesses a second 
long tooth. The galea is much reduced. 
The most striking feature of the labium is the unequal size of 
the glossae and the paraglossae. The glossae are reduced to small 
lobes, while the paraglossae are developed into very large lobes. 
The hypopharynx is normally produced to or beyond the tips of 
the glossae. 
The genera belonging to this family are such a varied lot that 
very little can be said about the general biology which will apply 
to the entire group. The majority of the genera are found in 
rather swift running water. . 
Genus PERLODES Banks 
Stoneflies of this genus are restricted to the Rocky Mountain 
region and the Western States. The nymphs are recognized by the 
presence of a pair of small, single, finger-like, tracheal gills which 
are attached to the outer, lower base of the submentum of the 
labium. In addition to this pair of gills, some species of the genus 
have the same type of gills on the conjunctivae on the ventral 
