TETRAGONEURIA 179 
The nymphs crawl over the bottom or clamber over loose trash and 
timbers. They are rather clean and hairless, and show when recently 
moulted a neat but rather obscure color pattern. The genus is widely 
distributed over North America. It is often very abundant about the 
wooded shores of lakes and ponds where cast skins of the transforming 
nymphs are sometimes found in almost incredible numbers 
The species are all about one size and one color pattern of body and 
are very variable in the markings of brown upon the wings. Many 
species have been named because of very slight differences. We can 
find no good use for all these names since our specimens seem to trans- 
gress all the boundaries that have been indicated. The last important 
paper on the genus is that of Muttkowski (1911) in which he endeavors 
to define eleven species. We recognize five, that are separable as fol- 
lows: 
KEY TO THE SPECIES 
Adults 
1 Wings with no. brown markings, 0: ws se anes stella, p. 181 
Wangs with: Drown viMarkame yc ors 81s! s Pete be 3% a, ghey eS oe 2. 
2 Frons with a T-spot above; triangle of the hind wings generally 
SB CEOGS VEU tc aes ite ie eeae a poeta tae ool suo e a es spinigera, p. 181 
Frons generally with no‘ T-spot above}........) ... ooe.ue. eras... 3. 
3 Abdominal appendages of the male straight..... cynosura, p. 180 
Abdominal appendages of the male angulated va bent downward 
Bt thie: tip. ofA uA eines Sey ee a eihead erie tor ators Nears og 4, 
4 Male inferior appendage extends beyond the angulation of the 
BUEN eo eae '9 oi iag tae eee ade eae ee spinosa, p. 181 
Male inferior appendage does not reach the angulation of the 
REBEMOD Mice ities tae oy te Ste eas bee ee ee canis, p. 181 
Nymphs 
1 Lateral spines of the 9th abdominal segment divergent strongly 
Ea i Riera ei Sth ae ede i SUE in ARE FORM ots pT Rai Ae 2 spinigera. 
Lateral spines of the 9th abdominal segment very slightly or not at 
MN ELVETZONG:.. os. chee ste osiccrc, cit es 6 Oe a ee 2. 
2 These spines distinctly longer than the body of the segment... . 
Dae tes WercadaQhyn ikl ine ca ralnarcas pat eee Ae OL ae ee cynosura. 
These spines distinctly shorter than the segment, and slightly in- 
gag ved: at ANG HPS tri cx-ourcerh arnt -yakhe Gb Rea ee ee canis. 
