34 
Psyche 
[March 
of the light and dark varieties showed no differences when 
reared, which further convinces me that they are the same 
species. 
The nymphs of E. rotunda seem remarkably varied in 
their choice of habitat. Although most usually found in the 
mud-gathering moss of flat rocks on the bottoms of fairly 
rapid streams, they were also collected in all intergrading 
types of streams from shallow riffles to the rather sluggish 
sections of deeper streams. This variety of habitat may be 
in part responsible for the variety of coloration and pattern 
displayed by this nymph, and even for some of the minor 
structural differences mentioned in the above descriptions. 
Ephemerella septentrionalis McDunnough 
Imago : 
Measurements: body 10 mm.; tails 12 mm; foreleg of 
male 16 mm., fore wing 10 mm. (Measurements of female 
same, except for foreleg). Compound eyes of the male 
orange-brown, thorax yellowish. First seven abdominal 
segments grayish, 8th yellowish-gray, 9th and 10th yellow. 
Head, thorax and abdomen of female yellow; legs yellow. 
Compound eyes grayish and small; ocelli reddish-brown. 
Subimago : 
Wings subhyaline. 
Nymph: 
Measurements : body 10 mm ; tails 7 mm ; foreleg 6 mm. 
Head smooth except for a tuft of hairs on either side of 
the mid-frontal line of the apex. General color of thorax 
and abdomen light brown with a narrow brown mid-dorsal 
line. A row of brown dots on either side the median ventral 
line of the abdominal segments, and one at the base of each 
leg on the ventral side of the thorax. Legs extremely long 
and slender in proportion to the body. Tarsi with a band of 
brown. Gills present on abdominal segments 3-7. Dorsal 
spines absent. Lateral spines on segments 4-9. Tails light, 
