May, 1953 
Known from Illinois and Indiana. Lives 
in shallow, rapid streams with sandy bot- 
toms. 
Illinois Records. — HiLispaLe: Rock 
River at mouth of Canoe Creek, dredging 
sandy bottom 15 yards from bank, July 30, 
1925, R. E. Richardson, 1g N; Rock River 
at foot of Lephardt’s Island, dredging clean 
sandy bottom 15 yards from bank, July 30, 
1925, R. E. Richardson, 1 ¢ N. 
16. LACHLANIA Hagen 
Lachlania Hagen (1868: 372). 
This genus is represented in North Amer- 
ica only by saskatchewanensis Ide (1941: 
154), described from a single adult female. 
Nymphs and adults of Lachlania sp. are 
recorded by Edmunds (19486:43) as oc- 
curring in Utah. 
In Lachlania adults, the fore wing, fig. 
182, has only three or four crossveins; vein 
M branches a little beyond mid-length, and 
veins Cu, and Cu, fork close to the wing 
base. The legs are, greatly atrophied and 
probably nonfunctional. The median caudal 
filament is vestigial. 
LEPTOPHLEBITIDAE 
This family corresponds exactly to the 
subfamily Leptophlebiinae of the family 
Baetidae in Traver’s classification (1935a: 
504), and to the family Leptophlebiidae of 
Ulmer’s classification (1933: 201). 
In this family, each compound eye in the 
adult males is composed of a large upper 
portion of comparatively large facets, and a 
small lower portion of smaller and darker- 
colored facets. These two portions of the 
eye are distinctly separated, but the upper 
portion is not set on a well-developed stalk, 
as in the Baetinae, figs. 255-257. The com- 
pound eye in the females is of the same size 
as the lower portion of the eye in the males. 
The fore tarsus in the males has five seg- 
ments; all tarsi in the females and the middle 
and hind tarsi in the males have four 
clearly differentiated segments. In all Ne- 
arctic genera, the two claws borne by each 
tarsus are dissimilar, with one claw hooked 
and one claw lobed. 
In all Nearctic genera of Leptophlebiidae, 
the adults have two pairs of wings; in some 
exotic leptophlebiids, the adults lack hind 
wings. The fore wings in Nearctic forms 
Burks: THE MAyFLigs oF ILLINOIS 81 
have numerous crossveins, figs. 185-192, 
and all the principal longitudinal veins are 
preserved complete, except that the basal 
part of vein M,, is obsolete in some genera. 
Vein R. often is sharply bent posteriorly 
near its base, that is, close to its point of 
divergence from R,, as in figs. 185-187. 
Veins Cu, and Cu, are separated at their 
bases; Cu, is straight, but Cu, at about 
mid-length is sharply bent toward the anal 
wing margin. There are two or four cubital 
intercalary veins. The hind wing may or 
may not have a costal projection. There is 
considerable variation within this family in 
the venation of the hind wing. 
The male genitalia are composed of a pair 
of elongate penis lobes, which are partly or 
completely fused on the mesal margins, and 
a pair of four-segmented forceps. The basal 
segment of each arm of the forceps is often 
almost completely fused with the second 
segment; the second segment is elongate and 
straight; the third and fourth segments are 
small and semiquadrate or triangular. The 
terminal abdominal sternite in the females 
usually has a median cleft or indentation on 
the posterior margin. There are always 
three well-developed caudal filaments; the 
median one may be somewhat shorter and 
more slender than the cerci. 
The nymphs, figs. 199, 212, are typically 
slender and somewhat flattened forms. They 
commonly inhabit still water or water with 
reduced current, such as that in eddies along 
banks of streams or rivers. The tarsal claws 
have minute, ventral denticles. Abdominal 
segments 1-7 bear gills; these gills are 
slender-lamelliform to filamentous, figs. 193— 
196. The nymphs always have three long 
caudal filaments, all of which have relatively 
inconspicuous setae uniformly distributed 
over the filaments. 
KEY TO GENERA 
ADULTS 
1. Hind wing without a costal angulation, 
and with costal margin slightly concave 
near mid-length, figs. 185-187...... 2 
Hind wing with a well-marked costal 
angulation, figs. 188-192 ... 
2. Fore wing with Cu; and Cup closer to- 
gether than Cu; and M in subbasal 
region where these veins are subparallel, 
figs. 185, 186.......17. Leptophlebia 
Fore wing with Cu; and Cus separated in 
subbasal region by a space equal to 
that separating Cu; and M, fig. 187... 
oe a Tne 18. Paraleptophlebia 
