94 Intinois NarurAL History SuRVEY BULLETIN 
forceps-like at the apex; the head is 
flattened; all the gills are double and lanceo- 
late, diminishing in size from abdominal 
segment | to 7; the posterolateral angles 
of abdominal segments 2-9 are produced as 
slender spines; the three caudal filaments 
are of the same length. These characters 
are drawn from Peruvian specimens in the 
Cornell University collection determined as 
of this genus by Needham & Murphy. 
Thraulodes speciosus Traver (1934:201), 
described from Texas, and arizonicus Mc- 
Dunnough (1942:117), from Arizona, are 
the only known Nearctic species. 
20. HABROPHLEBIA Eaton 
Habrophlebia Eaton (1881:195). 
The Nearctic species of Habrophlebia 
consist of small, slender mayflies with clear 
wings. The fore tarsus in the males is only 
two-thirds as long as the fore tibia; the 
tibiae of all legs in both sexes are con- 
spicuously long and slender, always much 
longer than the femora. All longitudinal 
veins of both wings, fig. 189, are hyaline or 
faintly tinted at the bases only; the cross- 
veins are all but invisible. Each fore wing 
has two long and two alternating, short 
cubital intercalaries, which are free at the 
bases; vein R. is slightly bent posteriorly 
near the base; vein M, diverges from M, 
near the base of the wing, but the basal part 
of M, is obsolete. The hind wing has a 
costal angulation, and vein Sc ends at or 
near the apex of the wing. The genital 
forceps arise from a _ medianly, deeply 
fissured base; the length of the apical two 
forceps segments combined is almost as 
great as the length of the long basal seg- 
ment. ‘The penis lobes are divided nearly 
to the base, fig. 213; each lobe bears a long, 
bladelike, apical appendage. The terminal 
abdominal sternite in the females is deeply 
cleft on the meson of the posterior margin. 
The median caudal filament is longer than 
the cerci. 
In the nymphs, the body is slender and 
only slightly flattened; the head is sub- 
triangular and is held in a somewhat prog- 
nathous position. The antennae are slender 
and each about as long as the head and 
thorax combined. The maxillary palp has 
three segments, and the labial has three. 
The tarsal claws are single and relatively 
short, and bear a single ventral row of 
Vol. 26, Art. 1 
denticles. Each of the gills, fig. 196, is 
single at the base, then quickly branches into 
two rami, each of which is then subdivided 
into three or more slender terminal fila- 
ments. The median caudal filament is longer 
than the cerci. 
This genus includes two Nearctic species, 
neither of which has yet been taken in 
Illinois. One of the two is, however, widely 
distributed and might eventually be found 
to occur here. 
Habrophlebia vibrans Needham 
Habrophlebia vibrans Needham (1908: 192). 
Habrophlebia jocosa Banks (1914:614). 
Mave.—Head and thorax dark brown; 
legs predominantly white; wings hyaline, 
A 213.—Habrophlebia vibrans, male geni- 
talia. 
Fig. 214.—Choroterpes basalis, male geni- 
talia,. 
