May, 1953 
Urspana: University Grounds, April 8, 
1889, Marten, 56; April 15, 1898, Hart, 
10¢. Warson: April 9-24, 1936, Ross & 
Mohr, 194 ; April 11, 1932, Ross & Mohr, 
Le 
18. PARALEPTOPALEBIA Lestage 
Paraleptophlebia Lestage (1917:340) ; 
Ulmer (1920a:113, 116). 
The genus Paraleptophlebia was originally 
distinguished from Leptophlebia in the 
nymphs only. Lestage’s description of the 
genus appeared in a study of the nymphs of 
Palearctic mayflies.5 Ulmer (1920c:113; 
1933: 202), however, gave characteristics for 
the separation of the adults of the two 
genera. Traver (1934:189; 1935a:510) 
transferred most of the American species of 
Leptophlebia to Paraleptophlebia. 
The adults of Paraleptophlebia are small, 
extremely frail mayflies. They have clear or 
faintly tinted wings and most of them have 
predominantly dark brown bodies; the males 
of some species have the middle abdominal 
segments mostly white. The fore wing, fig. 
187, has the posterior branch of the outer 
fork (vein R.) sharply bent posteriorly near 
the base, vein M, diverges from M, near the 
wing base, and the cubital intercalary veins 
are detached at their bases. The hind wing 
is broad and lacks a costal angulation, and 
vein M is forked near the base of the wing. 
The fore leg in the males has the tarsus 
one and one-half to two times as long as the 
fore tibia. The terminal abdominal sternite 
in the females is deeply cleft on the meson. 
The three caudal filaments are equal in 
length. 
The male genitalia in Paraleptophlebia, 
figs. 201-211, consist of a pair of slender 
penis lobes, which are more or less fused on 
the meson, and a pair of four-segmented 
forceps arising from a medianly cleft base. 
Each penis lobe bears one or two appendages. 
The shape and arrangement of these ap- 
pendages, as well as the shape of the penis 
lobes themselves, provide excellent charac- 
ters for the recognition of species. Some 
species also show striking differences in the 
form of the forceps. The male genitalia may 
be cleared, stained, and mounted on micro- 
scope slides for study, but the operation must 
be done with great care, as the minute, frag- 
ile genital structures of the males of this 
genus are easily broken or distorted. The 
Burks: THe MAyFLies oF ILLINOIS 87 
genitalia on many dry specimens are suitable 
for study without special preparation, and 
the same is true for specimens in alcohol. 
The agile nymphs, fig. 212, are small and 
rather flat dorsoventrally. In life, they hold 
their heads in a semihypognathous position. 
They are not strong swimmers, and are most 
often to be seen crawling among debris and 
gravel on the bottoms of shallow pools or 
eddies. They move with a characteristic, 
snakelike motion. 
In most species, the mouth-parts are sim- 
ilar to those to be found in most heptageniid 
nymphs. There are three segments in each 
labial palp and three in each maxillary palp. 
Also, in most species, each mandible is short 
and terminates in two or three toothed in- 
cisors. In a few western species, however, 
the body of the mandible is greatly elongated 
and tusklike, projecting anteriorly far past 
the labrum. In the species with tusked man- 
dibles, the left mandible retains two incisors 
while the right has but one. Each antenna 
is as long as the head and thorax combined. 
The tarsal claws are single, slender, and 
long, with numerous ventral denticles. Each 
of abdominal segments 1—7 bears a pair of 
bifid, filamentous gills, all of which are of 
the same type, fig. 194. The posterolateral 
angles of abdominal segments 8 and 9, or 9 
only, are produced as slender spines. The 
three caudal filaments are of about equal 
length. 
Nymphs of this genus develop principally 
in shallow, fairly rapid streams of small or 
moderate size. These streams usually have 
bottoms of coarse gravel. 
The key to nymphs given below is based 
on a study of nymphal material in the 
Cornell University collection and the ma- 
terial reared in Illinois. Gordon (1933: 
116) and Traver (19354:514) have pub- 
lished keys for the nymphs of Paralepto- 
phlebia, and Ide (1930b:207) has published 
descriptions and figures of the nymphs of 
several northeastern species. 
Specific characters for the separation of 
females of this genus have not yet been 
found. 
KEY TO SPECIES 
Aputt MALeEs 
1. Forceps with a large, dorsal enlargement 
near base, visible in lateral aspect, 
figcey 2 ite Sirah Vox ss oko ate tg: = 2 
Forceps without a large, dorsal enlarge- 
Ment near bases semis aA se 3 
