84 
wa 
6. 
ILLINOIS NATURAL 
Vein M of hind wing forked, fig. 188. 
Ser Sees SAL has ane re 19. Thraulodes 
Vein M of hind wing simple, figs. 189- 
| Tae gachar Bp aire pcre Ga thin a>, + 
Vein Sc of hind wing extending nearly or 
quite to apex of wing, fig. iC eum 
20. Habrophlebia 
Vein Sc of hind wing ending near costal 
angulation, figs. 190-192. 
Costal angulation of hind wing small, 
rounded at apex, fig. 190; penis lobes 
simple, without appendages, fig. 214. 
21. Choroterpes 
Costal angulation of hind wing prominent, 
almost or quite acute at apex, figs. 191, 
192; penis lobes bearing decurrent ap- 
pendages, FiSe oS PS 20 big cee Re 6 
Male forceps base divided into two tri- 
angular lobes; decurrent appendages of 
penis lobes projecting anterolaterally, 
fig. 215; costal projection of hind wing 
finger- like, stubby at apex, fig. 191. 
ek Habrophlebiodes 
Male forceps base entire, not divided into 
triangular lobes; decurrent appendages 
of penis lobes projecting toward meson, 
and a pair of slender i ye aris- 
ing from forceps base, fig. 216; costal 
angulation of hind wing acutely pointed 
at apex, fig. 192... .... 23. Traverella 
Matrure Nympus 
Gills of first abdominal segment similar 
in type to gills borne by more posterior 
segments, as in figs. 194, 196........ 2 
Gills of first abdominal segment of a differ- 
ent type from gills borne by more 
posterior segments, as in figs. 193, 195; 
each gill of first pair filamentous, each 
gill of following pairs double and lamel- 
ET aR Nee eter NBR ane Ma ml 6 
Abdominal segments 2-9 with postero- 
lateral spines......... 19. Thraulodes 
Abdominal segments 8 and 9 only bearing 
posterolateral’spines. | os 7.ca8u eee 3 
Each abdominal gill lamelliform, the 
margins of each finely dissected to form 
numerous, long filaments; gills on 
segments 1-5 bilamellate; gills becom- 
ing progressively smaller from anterior 
to posterior abdominal segments...... 
bated ear eens Biles TeeaON 23. Traverella 
Each abdominal gill not lamelliform, the 
margins not finely dissected........ 4 
Gills on abdominal segments 2-7 each 
consisting of two clusters of slender 
filaments borne on a single, narrow 
stalk, fig. 196...... 20. Habrophlebia 
Gills on abdominal segments 2-7 bifid to 
bases, each part a very slender la- 
reiey |e Esky eT OR U2)” ORR + eaten es ci Pe 
Apical margin of labrum only slightly in- 
dented on jee os. 197 
Paraleptophlebia 
Apical margin of rede deeply indented 
DM pINeSON. O87 L9e) ory ogee ee 
RS Ae 22. Habrophlebiodes 
Each gill of pair borne by first abdominal 
segment a single filament; apical ex- 
tensions of gills on segments 2-7 some- 
History Survey BULLETIN 
Vol. 26, Art. 1 
what spatulate at apexes, fig. 195. 
EVA RU ap yer telietign gag 21. Choroterpes 
Each gill of pair borne by first abdominal 
segment bifid at apex; apical extensions 
of gills on segments 2-7 slender, acute 
at apexes, fig. 193...) 5 See 
17. LEPTOPHLEBIA Westwood 
Leptophlebia Westwood (1840:31). 
Blasturus Eaton (1881:193). 
Euphyurus Bengtsson (1917:177). 
In accordance with the researches of Ide 
(1935a: 123), the American species formerly 
placed in Blasturus are now placed in Lepto- 
phlebia. It may be noted that Banks (1900: 
245) published this synonymy much earlier. 
The members of this genus are medium to 
large mayflies with predominantly dark 
yellow-brown bodies. The fore tarsus in the 
males varies from one to one and two-thirds 
times as long as the fore tibia. The wings, 
figs. 185, 196, are clear or partly stained 
with brown, and all veins and most cross- 
veins are brown. In the fore wing, the 
posterior branch of the outer fork (vein R,) 
is sharply bent posteriorly near the base, 
vein M, diverges from M, in the subbasal 
region, the basal costal crossveins are weak 
or wanting, and there are two long, cubital 
intercalary veins. The hind wing has no 
costal angulation, and vein M is forked near 
the base of the wing. 
The male genitalia, fig. 200, are quite 
uniform in structure throughout the genus. 
The genital forceps arise from a medianly 
fissured base and have four or five segments, 
of which the apical two are minute. The 
penis lobes are fused on the meson at the 
bases only; each penis lobe bears a stout, 
mesal, decurrent appendage. The position of 
the apexes of these appendages determines 
whether they look like a “scarf” or a 
“hood”; actually the structure of these ap- 
pendages is very similar throughout the 
genus. The terminal abdominal sternite in 
the females has a triangular, median notch 
on the posterior margin. The three caudal 
filaments may be equal in length and thick- 
ness or the median filament may be slightly 
shorter and weaker than the cerci. 
The stout-bodied nymphs, fig. 199, are 
vigorous swimmers. The thorax and ab- 
domen are slightly flattened on the dorsum, 
but the head is held almost in a hypognathous 
position. Each of the maxillary and labial 
: 
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