May, 1953 BurRKS: 
quite low; its height is only about one-half 
as great as the diameter of the lower portion. 
Each arm of the genital forceps, fig. 299, has 
the basal segment broad and short, the 
second segment semiquadrate, with a large 
projection on the median margin, the third 
segment long, relatively stout, and very little 
bowed, and the fourth segment two and one- 
half to three times as long as broad. The 
penis cover is produced on the meson. 
The nymphs have long, three-segmented 
maxillary palps, the labial palps are broad, 
truncate, and three-segmented; the tarsal 
claws are long, slender, and nondenticulate ; 
the abdominal gills are single and platelike, 
and they bear blackened tracheae which 
branch on the inner sides only; the three 
caudal filaments are well developed. 
Neocloeon alamance Traver (1932:365), 
originally described from North Carolina 
and later recorded from Tennessee, is the 
only known species in this genus. 
35. CLOEON Leach 
Cloeon Leach (1815: 137). 
Cloea Billberg (1820:97). Emendation, 
unnecessarily proposed. 
Cloe Burmeister (1839:797). Emendation, 
unnecessarily proposed. 
Chloeon Lubbock (1863:61). Emendation, 
unnecessarily proposed. 
Cloeopsis Eaton (1066:146). 
Procloeon Bengtsson (1915:34). 
synonymy. 
New 
In species of the genus Cloeon, the fore 
wing has relatively few crossveins and only 
a single marginal intercalary vein in each 
interspace of the outer wing margin; the 
hind wings are wanting. 
In the males, the fore tarsus is approxi- 
mately equal in length to the fore tibia, and 
either one is slightly longer than the fore 
femur. The hind tarsus has the partly dif- 
ferentiated first segment as long as, or 
slightly longer than, the two apical tarsal 
segments combined. Each arm of the genital 
forceps, fig. 300, has the first segment broad, 
short, and narrowed at the apex; the second 
segment is somewhat conic and not clearly 
separated from the third segment; the third 
segment is long, slender to fairly stout, and 
usually slightly bowed; the fourth segment 
is about as broad as long. The penis cover 
is usually truncate at its apex. 
Both maxillary and labial palps in the 
nymphs have three segments; each tarsal 
THe Mayr ties or ILLINois 141 
claw is relatively short, broad at the base, 
and slender at the tip, and bears a single 
row of minute ventral denticles; the ab- 
dominal gills are sheetlike, undulated, and 
double, with the tracheae usually branching 
palmately; the three caudal filaments are 
well developed. Mayflies of this genus, so 
far as is known, develop in small ponds or 
in the still eddies along the banks of streams. 
Cloeon includes 10 described Nearctic 
species, 8 of which are treated here. The 
species of Cloeon all seem to be quite rare 
in eastern North America. 
Reliable characteristics for the specific 
determination of the females and nymphs 
in this genus have not yet been found. 
KEY TO SPECIES 
Apvutt Mates 
1. Abdominal tergites 2-6 almost entirely 
dark red-brown or gray-brown...... 2 
Abdominal tergites 2-6 hyaline, white or 
faintly yellowish, often with red or 
dark brown, markings. -.: 2405.4 oe 3 
Caudal filaments white, stained with red- 
brown at bases, but articulations not 
darkened; abdominal tergites 2-6 light 
PTAy< LOW ween ee ee 1. ingens 
Caudal filaments white, with articulations 
dark brown or black throughout; ab- 
dominal tergites 2-6 almost entirely 
dark red-brown......... 2. dipterum 
3. Abdominal tergites 2-6 uniformly stained 
with light red, without darker markings 
Fa ee ER ba i ee a Seno 3. mendax 
Abdominal tergites 2-6 hyaline, white, or 
faintly yellow, often with red or dark 
brOWNEMarkInGSe,- oyy. cede ee 4 
4. Abdominal tergites 2-6 hyaline, with a 
pair of large, lateral, dark brown 
blotches on each, these blotches on seg- 
ments 3 and 6 so large as to coalesce on 
to 
MESON Wael wig te er oy: 4. minor 
Abdominal tergites 2-6 white or light yel- 
lowish, without large, lateral, dark 
brown blotches, but sometimes with 
small, red marks on some or all of these 
TERZILES a So R ee err eeee ee ee 5 
5. At least some of abdominal tergites 2-6 
with small, red markings............ 6 
Abdominal tergites 2-6 white, without 
red tmarkings.ea eng ae Soak Parse he ok: v | 
6. Abdominal tergites 2 and 3 each with 
a faint, median, red streak........... 
....5. insignificans 
Posterior ‘margin “of each of abdominal 
tergites 2-6 with a pair of submedian, 
ted dashes’. 6. rubropictum 
Mesonotum light yellow-brown......... 
Better e aerate aes re a eo 7. vicinum 
Mesonotum dark brown, shading to 
creamy white at lateral margins and at 
apex of scutellum......... 8. simplex 
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