VOL. 54, NO. 1, JANUARY 1978 
21 
In the material I have examined, both E. inermis and E. infrequens 
may have paired submedian spots on the posterior margin of the 
abdominal terga, but the spots are variable and often indistinct or 
absent. The color is similar and extremely variable in the two species; 
body coloration is usually light to dark reddish or chocolate brown 
with variable pale markings, but it is not uncommon to find 
specimens that are uniformly pale or concolorous dark brown. Legs 
are usually pale with conspicuous dark bands but also may be con¬ 
colorous. 
Allen and Edmunds (1965) and Jensen (1966) have noted that the 
larvae of E. inermis often have small paired undulations or proturber- 
ances on the posterior margin of some abdominal terga, and use the 
presence of the character to identify the species. My observations 
indicate this character occurs with equal frequency in both species. 
The new characters described below, which are differences in leg 
armature and claw morphology, show consistent interspecific differ¬ 
ences. Mature larvae of both E. inermis and E. infrequens have one or 
more rows of spines on the posterior margins of the femora (Figs. 2a, 
c). However, the spines of E. infrequens are generally .07-.09 mm or 
longer (Fig. 2a). This is considerably longer than those of E. inermis 
which are usually .02-.05 mm long with only a few as long as .06-.07 
mm (Fig. 2c). E. infrequens also has a distinct subapical band of 
spines on the dorsal surface of the forefemora (Fig. 2a) while E. 
inermis has no band or at most a sparse indistinct subapical band 
consisting of only a few spines (Fig. 2c). Also the rows of spines on 
the posterior margin of the forefemora of E. inermis may be incon¬ 
spicuous or absent (Fig. 2c). 
The least variable difference between the larvae of these two 
species is the shape of their claws. Both E. inermis and E. infrequens 
have claws with 7-10 denticles. However, the anterior margin of the 
claw of E. inermis is strongly curved between the most distal denticle 
and the tip, often with an arc of 90 degrees or more (Fig. 2d). In 
contrast the claw of E. infrequens is very gently curved in this region 
(Fig. 2b). 
Characters common to Ephemerella inermis and E. infrequens 
Mature larva. General body color either uniform light to dark 
reddish or chocolate brown, or light to dark reddish or chocolate 
brown with highly variable pale markings. Head brown with variable 
pale markings at vertex. Thoracic notum brown with variable pale 
sinuate markings; lateral margin of pronotum usually pale; femora 
pale with variable brown markings; posterior margins of femora with 
one or more rows of spines; tibiae concolorous pale or pale to light 
brown with one basal and one midlength dark brown band; tarsi 
uniformly pale or pale to light brown with basal dark brown band; 
