60 THOMAS SAY FOUNDATION 
Key to the known Species of Alloperla 
1. Eastern forms—length up to 9mm... 7. mediana (p. 61) 
Western forms—various lengths...) .. 2. 2. 4...) eee 2 
2. Length up to 13 mm.; cerci not more than 14 the length of 
bod yet i sr Sn ed eee borealis (p. 60) 
Length under 13 mm.; cerci often more than 1% the length of 
body a0) Ut oe Le 3 
3. Small yellowish nymphs not over 7 mm. long when fully 
GROW (ieee | vein cs CR et ee Oe eee pallidula (p. 62) 
Fully grown nymphs more than 7 mm. in length ......... 4 
spatulata (p. 62) 
coloradensis (p. 60) 
lamba (p. 61) 
Alloperla borealis Banks 
(Plate 6, figs. 89-93; plate 17, fig. 192.) 
Length of body up to 18 mm.; antennae up to 4 mm.; cerci 
up to 3 mm. 
This is the largest species of the genus. General color lght 
brown with portions of head, thorax, and abdomen shaded with 
darker brown. Head brownish with a small lighter area in front 
of the anterior ocellus, and with a more or less continuous trans- 
verse lighter band extending across the head from eye to eye; 
labrum lighter at base. 
Pronotum transversely suboval; surface hairy, with long hairs 
on the margin; meso- and metanotum and wing pads hairy. Legs 
somewhat flattened and covered with short hairs, but without dis- 
tinet fringe of long hairs on the outer margin of either femora 
or tibiae. 
Abdomen hairy and quite uniformly brown. Cerci short, rather 
thick at the base and tapering to a slender tip; thirteen to fifteen 
segments. Gills absent. 
The large size and the relative shortness of the cerci differen- 
tiate borealis from related forms. Described from mature nymphs 
from Temple Forks, Logan River, Utah, June 20, 1926. J. G. 
Needham. 
Alloperla coloradensis Banks 
(Plate 6, figs. 83-88.) 
Length of body up to 10 mm.; antennae up to 3.5 mm.; cerci 
up to 3 mm. 
General color yellowish brown, with the marginal groove of the 
