BURROWING MAYFLIES. 277 
KEY TO THE NORTH AMERICAN GENERA OF THE SUBFAMILY EPHEMERINA. 
A. Adults. 
1. The posterior fork of the median vein in the fore wing very deep, almost reaching the base of the 
wing; two long simple intercalary veins between the first and second anal veins...... CaMPSURUS. 
The posterior fork of the median vein not extending more than three-fourths the distance to the 
Hase of the ‘wing..S2a20. See tt ANA OT SG PAIE ENS & MEP ONE Be ACN SOIT SRA Boies oe 2. 
2. Between the first and second anal veins is a bunch of three or four long, straight, intercalary veins 
conjoined basally before their attachment to principal veins; the second anal vein is nearly straight, 
andgatibrahcheditye3s..228 Stat. 2021S BERS, RELA. ARR ER AL DI BO POLYMITARCYS. 
Between the first and second anal veins are only shorter, sinuate, and sometimes forking intercalary 
veins, that are attached directly to the first anal vein; the second anal vein is sinuate and often 
3. The posterior fork of the median vein extends two-thirds to three-fourths the distance to the base 
of the wing; vein Cu, not more strongly curved at the base than is the first anal vein. .EUTHYPLOCIA. 
The posterior fork of the median vein less deep, not longer than its stem; vein Cu, more strongly 
curved:at-its:tbase thanasthe fitst/analiveim isis. oniwael.ctaheraige. att an cond. deal. gees... 4- 
4. The third anal vein not forked, but attached to the hind margin of the wing by a series of cross veins; 
forceps of the’ male’4-jointed sia d3 gett woth GALICIA SCO « «208s oe se cede centages cs 5- 
The third anal vein ends in a single fork and is not attached to the hind margin of the wing, though 
a few isolated intercalated veinlets lie between; male forceps 3-jointed........... POTAMANTHUS. 
5. Tails 3 in male and female; fore wings with a definite and beautiful pattern of spots. . EPHEMERA. 
Tails 2 in the male; fore wings diffusely marked or plain........ 0.0.0... cee cece cece 6. 
6. Tails 3 in the female; mature color predominantly yellowish ..................... PENTAGENIA. 
Tails 2 in the female; mature color predominantly brownish ....................... HEXAGENIA. 
B. Nymphs. 
ye vUnksiown" (tropical and! subtropical) Aor. Jeo, OT I SB, POR 2B s CampsuRUS. 
Mandibular tusks shorter than the head, only their tips visible from above........ PoTAMANTHUS. 
Mandibular tusks longer than the head and very comspicuous........... 00.0000 ee cece ee eeees 2 
2. Front of head rounded; legs decreasing in length posteriorly; fore legs longest................... Ze 
Labrum wider than long; tusks hairy almost to tips ............. cc cee ee eee eee EUTHYPLOCIA. 
3. Front of head produced forward and conspicuously lobed; legs increasing in length posteriorly.... 4. 
Labrum longer than wide; tusks hairy only atenlarged base...................0020. POLYMITARCYS. 
aa hrantalspronunencessemucitcttiar, Smeliice 5.51) oi. eis weston cone cee seins seleelcadees HEXAGENIA. 
rantal aramiisienice: Dindvat ats iD sia daida le oe a aati ae Wigan Heels ohm ae es byeiiansts S: 5- 
5. Both mandibular tusk and frontal prominence denticulate extermally.............. PENTAGENIA. 
Mandibular tusk and frontal prominence smooth externally ..............-.200---00005 EPHEMERA. 
SINGLE DISTINCTIVE CHARACTERS OF OUR GENERA OF &PHEMERINA. 
So well marked are these genera that they may be recognized at a glance by the following characters: 
Adults. 
EPHEMERA alone has the fore wings ornamented with a pattern of transverse spots. 
HeEXAGENIA alone has a border of brown on the front of the fore wing and another on the outer 
margin of the hind wing. 
PENTAGENIA alone has the transverse row of four dots on the veins, as shown in Plate LX XIII, fig- 
ure 15, and a single conspicuous dorsal stripe laid lengthwise of the body. 
CampsuRus alone has the middle and hind legs aborted, also the greater depth of the posterior 
fork of the median vein, almost reaching the wing base. 
PoTAMANTHUs is the smallest (expanse of wings about three-fourths of an inch), and it alone has 
the wings wholly transparent (the two following white-winged genera have gray or purplish margined 
fore wings). 
