157 

 Jewett: Plecoptera 



opening of an aquatic net or fine-meshed sieve. An 

 excellent source of nymphs is among the debris which 

 collects at grills at water diversion structures. Nymphs 

 may be reared by placing them in small wire cages 

 fixed to a floating raft in streams in such a manner 

 that the upper part of each cage is above the water 

 level (Frison, 1935a, pp. 305-307). 



TAXONOMIC CHARACTERS 



As indicated in the following keys, wing venation, 

 gills, number of ocelli, and male genitalia are the 

 principal morphological features used in classifying 

 stoneflies above the species level. The genitalia of 

 both sexes, but particularly those of the male, are 

 used primarily for differentiating species. The dorsal 

 color patterns of the head, thorax, and abdomen are 

 very useful in classifying the Setipalpia and are 

 specifically distinct for many species. The mouth 

 parts and chaetotaxy of nymphs seem to be distinctive 

 for most species, but the association of nymphs with 

 adults is best accomplished through rearing. Where 

 external gills occur, nymphs may sometimes be asso- 

 ciated with adults of the same species, since remnants 

 of nymphal gills persist in the adult stage. 



Usually clearing of genitalia in adults is unneces- 

 sary in studying stoneflies if the specimens have 

 been preserved correctly in alcohol. Exceptions occur 

 with some of the smaller species, with dry or poorly 

 preserved alcoholic specimens, and with genera where 

 the aedeagus is useful or necessary for specific 

 identification. The mouth parts of nymphs should be 

 cleared. Clearing is easily accomplished by placing 

 the mouth parts or the terminal third of the abdomen 

 in 10-15 per cent KOH. Softening of the nonsclero- 

 tized parts is usually accomplished within twenty-four 

 hours, and these can be removed; heating the KOH 

 will greatly speed the process. After several baths 

 in distilled water, the structure may be placed in a 

 small shell vial which may be kept in the larger vial 

 containing the rest of the specimen. 



Key to the Families and Genera of North 

 American Plecoptera Adults ' 



1. Paraglossae and glossae of about equal length (fig. 

 6:4a) suborder FILIPALPIA 2 



— Paraglossae much longer than the glossae (fig. 6:46) 



suborder SETIPALPIA 16 



2. Abdomen without branched gills on the ventral side; 

 anal area of fore wing without cross veins or with only 

 1 row of them 3 



— Branched gills on the ventral side of abdominal seg- 

 ments 1 and 2; anal area of fore wing with 2 or more 

 full rows of cross veins PTERONARCIDAE 15 



3. Form cockroachlike (fig. 6:5); ocelli 2; at least 10 

 costal cross veins in fore wing 



PELTOPERLIDAE Peltoperla Needham 1905 



— Form typical; ocelli 3; less than 10 costal cross veins 

 in fore wing except in Isocapnia which may have 10 or 

 more NEMOURIDAE 4 



4. Second tarsal segment much shorter than the first (fig. 

 6:6a) 5 



'Adapted largely from Flicker (1943, 1952). 



Fig. 6:4. Ventral view of nymphol labium, a, Taeniopteryx maura; 

 b, Isoperla pafricia (a, Frison, 1935; b, Frison, 1942b). 



— Second tarsal segment at least as long as the first 

 (fig. 6:66) TAENIOPTERYGINAE 14 



5. Wings lying nearly flat when at rest; second anal vein 

 of fore wing forked (fig. 6:76); cerci 1-segmented 



N'EMOl.'UINAE Nemoura Pictet 1841 



— Wings either rolled around the body at rest, or wings 

 flat when at rest and with second anal vein of the fore 

 wing simple; cerci either 1-segmented or with more than 

 4 segments 6 



6. Wings rolled around the body; intercubital cross veins 

 of the fore wing usually more than 5 (fig. 6:7a); second 

 anal vein of the fore wing forked; cerci 1-segmented 



LEUCTRINAE 7 



— Wings flat; 1, or rarely 2, intercubital cross veins in 

 the fore wing (fig. 6:7e,/-A); 2nd anal vein of the fore 

 wing simple; cerci with at least 4 segments 



CAPNIINAE 9 



7. Veins Rs and M in the fore wing with a common origin 

 on R (fig. 6:7d); male 9th sternite greatly produced, 

 sharply upturned and fingerlike at the tipj 7th 



Fig. 6:5. Nymph of Peltoperla brevis (Frison, 1942b). 



