BURROWING MAYFLIES. 283 
segment. There is an angulate line of long, thin hairs extending across the tibia near its base on the 
inner side. These hairs are outspread, fanlike beneath the mouth, meeting from the two sides, and may 
serve as a sort of table to hold up. the food convenient to the jaws. The front tarsus is hardly longer than 
the tibia is wide; its claw, a third as long, is short and thick and curved and abruptly tapering. Middle 
and hind legs are more slender and less hairy; third tarsi are longer, with claws of equal length, more 
slender and tapering. 
The wings of the nymph show four round, black spots at the points where dots will appear in the 
wing of the adult (see Pl. LXXIII, fig. 15), and two additional larger pigment spots that do not re- 
appear in the adult—one on the posterior fork of the median vein and one on the rear end of the humeral 
cross vein. 
The abdomen is nearly cylindrical, nearly covered above by the bushy, purplish gills. The 
lateral margins of segments 3 to 7 just outside the gill bases are expanded with bluntly rounded, lateral 
lobes that are densely clothed externally with golden-yellow hairs. These lobes increase in size to the 
fourth segment and then diminish in size posteriorly. The two divisions of the gill are unequal, the 
posterior being reduced in length, especially on the anterior gill-bearing segments. ‘The tails are rather 
short and stout and thickly fringed with hairs. 
EPHEMERA, the Mackerels. 
This is a genus of beautiful mayflies, somewhat smaller in size than the two pre- 
ceding, with relatively longer fore legs and tails. The cross veins of the front and 
middle portions of both wings are bordered with brown, and on the middle of the fore 
wing the brown is confluent in a series of spots arranged in a beautiful pattern. (See 
Pl. LXXV.)_ By this pattern our adult mackerels may all be easily recognized. 
The mackerels are lacustrine rather than fluviatile in habitat, especially E. simulans. 
The shores of the Great Lakes swarm with this species during early July, and on the 
Finger Lakes of New York they are only a little less abundant. 
The poorly differentiated species, E. varia Eaton, seems to prefer the little lakes 
and ponds and the muddy pools of stream beds. 
I have already published a description and figures of the nymph of E. varia (1901, 
p. 429). Miss Morgan has also figured it (1913, Pl. XLIV, fig. 8) and has added the 
following interesting notes on the habits of the species at Ithaca (p. 100) : 
No Ephemera nymphs were found in lower Fall Creek up to this time, that cleaner portion being 
nearly devoid of mud. On the first of July, however, the water in Beebe Lake was allowed to run off, 
bringing into the Lower Creek large quantitiesof mud. Three days later the shores below the dam were 
again examined. ‘Tracks similar to those made by earthworms covered the bottom near the shore line. 
Nymphs were crawling over the surface and sete could be seen projecting from many burrows. From 
an area of about 10 square feet 30 nymphs were removed. 
From this it appears that this species seeks out the muddy pools in even so turbulent 
and rocky a stream as is Fall Creek. 
E. varia is but doubtfully distinct from E. simulans. The wings of the typical form 
are less suffused with brown; the tip of the penis is a little more squarely truncated, 
and the proportionate length of the segments composing the forceps is slightly different; 
but none of these differences is either very tangible or very constant. I present new 
figures of the adult of E. varia on Plate LX XV, of its nymph on Plate LX XVI, and of 
the male genitalia of the three nominal species of the northern United States (these 
two and the very distinct E. guttulata) on Plate LX XXI, figures 58-60. 
Concerning the habitat and habits of the beautiful, but rare, broader-winged species 
E. guitulata Pictet no information is available. I have not seen that species alive, 
and the only specimen I possess is a fine male that was collected for me. 
110307°—21——_19 
