42 ILuinois NaTurAL History Survey BULLETIN 
white; hind wing with membrane and veins 
hyaline, and crossveins black, figs. 86, 87. 
This is the only species of Hexagenia so 
colored. 
NympH.—Length of body of 
specimen 22-28 mm. Apex of frontal proc- 
ess of head bluntly angled on meson, broad 
at base, fig. 72; mid-tarsal claw elongate, 
slender, fig. 79. 
Known from Illinois, lowa, Kansas, Man- 
itoba, Michigan, Missouri, New Brunswick, 
New York, Ohio, Oklahoma, Ontario, 
Pennsylvania, Quebec, and Vermont. De- 
velops in moderate-sized rivers that have 
a fairly rapid flow. 
Illinois Records.—Specimens, collected 
from April 26 to September 6, are from 
Aroma Park, Aurora (Fox River), Beards- 
town, Chicago, Dixon (Rock River), 
Homer, Kankakee (Kankakee River), 
Libertyville, Mahomet, Momence, Oak- 
wood, Oregon, Prophetstown, Rockford, 
Rockton (Rock River), Roscoe (Rock 
River), Rosiclare, South Beloit, White 
Heath, and Wilmington. 
mature 
6. Hexagenia recurvata Morgan 
Hexagenia recurvata Morgan (1913:395). 
This species has the wing membranes so 
heavily tinted with dark brown that freshly 
killed specimens appear to have almost black 
wings. The dorsum of the thorax is mostly 
very dark brown, but the abdomen is mostly 
light yellow, with relatively small, darker 
markings; the male genitalia are distinctive, 
fig. 73, as the penis lobes have their apexes 
recurved. The nymph differs from all others 
in the genus in having the first pair of ab- 
dominal gills single. 
Known from Maine, Massachusetts, 
Michigan, New York, North Carolina, On- 
tario, Quebec, and West Virginia. 
NEOEPHEMERIDAE new family 
This family includes a_ single North 
American genus, Neocphemera, which I am 
segregating from the Ephemeridae. Al- 
though the adults of Neoephemera show con- 
siderable similarity to the typical ephemerids, 
the nymphs are very similar to the caenid 
type. This indicates that Neoephemera is 
an interstitial form. Rather than include it 
in either the Ephemeridae or the Caenidae, 
necessitating the inclusion of a number of 
Vol. 26, Art. 1 
exceptions in the characterization of each 
family, I believe Neoephemera can better 
be considered as representing a_ distinct 
family. Ulmer (1933:199) placed Neoe- 
phemera in the family Ephemeridae, as did 
Traver (1935a:289). In describing the new 
Javanese genus Neoephemeropsis, Ulmer 
(1939: 481, 483; 1940: 606) pointed out that 
it is a near relative of the American gen- 
us Neoephemera and placed it in his fam- 
ily Potamanthidae. Neoephemeropsis almost 
certainly belongs in the family Neoephemeri- 
dae. The European form that is known as 
Caenis maxima Joly (1870:144) probably 
also belongs here. 
8. NEOEPHEMERA McDunnough 
Neoephemera McDunnough (19255: 168). 
Oreianthus Traver (1931a:103). 
New synonymy. 
In the adults of this genus, the fore 
wing, fig. 28, has the basal costal crossveins 
weak or entirely absent, the stigmatic cross- 
veins partly anastomosed, vein M, slightly 
curved toward vein Cu, near the wing base, 
two long, forked, cubital intercalary veins, 
and vein 1A with one to three crossveins 
extending from it to the anal wing margin. 
The hind wing has an acute marginal pro- 
jection, and veins M, and M, diverge near 
the center of the wing. The median caudal 
filament is well developed in both sexes. It 
may be noted that, in Neoephemeropsis, the 
median caudal filament is rudimentary in 
both sexes. 
The nymphs, fig. 88, are typically caenid in 
type, although each possesses two pairs of 
wingpads. Each tarsal claw is long, slender, 
and edentate, fig. 92. There is a minute, 
median, backward-projecting spine on the 
posterior margin of dorsum of the meta- 
thorax and on each of abdominal tergites 
1-2 and 6-8. Each gill of the pair on the 
first abdominal segment is minute, single, 
and filiform, fig. 898; on second segment 
elytroid, connate, covering the gills of the 
four following abdominal segments, and 
bearing a ventral tuft of filaments, fig. 894 ; 
on segments 3-6, fig. 89C, similar in form to 
the corresponding gills in Caenis, fig. 91D, 
but differing in that each dorsal, platelike 
gill has a ventral tuft of filaments near the 
base. The median caudal filament is well 
developed and all three caudal filaments 
are uniformly clothed with short spines. In 
