May, 1953 
sternite produced as a broadly rounded lobe, 
without median emargination or excavation; 
caudal filaments faintly tan stained on basal 
articulations. 
Known from Illinois and Iowa. 
Illinois Records. — Mount CarMet: 
Wabash River, June 10, 1947, Burks & 
Sanderson, 1¢. Orecon: Rock River, July 
fo25. L.H. Frison, 1¢, 12. Rock Is- 
LAND: 106, 92 (Walsh 1863:204). Rec- 
ords of supposed nymph: Dixon: Rock 
River, May 22, 1925, D. H. Thompson, 1 N. 
Mount CarmMeL: Wabash River, May 25, 
1942, Mohr & Burks, 1 N; May 28, 1942, 
Mohr & Burks, 1 N. 
48. ARTHROPLEA Bengtsson 
Arthroplea Bengtsson (1908:239). 
Remipalpus Bengtsson (1908:242). 
Haplonia Blair (1929:254). 
In the adult males of Arthroplea, the 
compound eyes are almost contiguous on the 
meson; the first fore tarsal segment is two- 
thirds as long as the second segment, and 
the entire tarsus is twice as long as the fore 
tibia. In both sexes, the venation of the fore 
wing is typical for the family, with the basal 
crossveins in the costal interspace rather 
weak and the stigmatic costal crossveins well 
developed but relatively few in number and 
not anastomosed. The hind wing, fig. 321, 
has the vein Rus unbranched throughout 
its length. The male genitalia, fig. 393, 
consist of a pair of five-segmented forceps 
and a pair of semirectangular penis lobes; 
each lobe bears three long, filamentous ap- 
pendages. In the females, the apical abdom- 
inal sternite has the posterior margin evenly 
rounded from side to side, not indented 
on the meson. 
The nymphs, fig. 395, are unique among 
American mayflies in that the labial and 
maxillary palps are considerably lengthened. 
Each maxillary palp has two segments and 
is as long as the head and thorax combined; 
each labial palp has two segments and _ is 
one-half as long as the maxillary palp. Nor- 
mally, the maxillary palps are held extended 
posteriorly, over the thoracic notum, but the 
labial palps are concealed beneath the head. 
Each tarsal claw is short, stout at the base, 
and bears a row of minute bristles on the 
Burks: THE MAyYFLies oF 
ILLINOIS 201 
eA 
te 
i, 
pe? 
gies 
Fig. 395.—Arthroplea bipunctata, mature 
nymph, dorsal aspect. 
ventral side in the basal area. A pair of 
single gills is present on each of abdominal 
segments I—7; each gill is platelike, with a 
point at the apex. There are three long 
caudal filaments. 
Arthroplea is represented by only one 
North American species, bipunctata (Mc- 
Dunnough) (1924c:76), known from Con- 
necticut, Maine, New Hampshire, Ontario, 
and Quebec. 
