26 
Ittinoris NaturAL History Survey BULLETIN 
can be seen clearly in the living adult male 
siphlonurines. 
i] 
KEY TO FAMILIES 
ADULTS 
Lateral ocellus in both sexes extremely 
large in comparison with a compound 
eye; each ocellus approximately one- 
half as large as a compound eye...... 
Bees in tenis a la Te ee 9 Caenidae, p. 43 
Lateral ocellus in males never more than 
one-tenth as large as a compound eye; 
in females lateral ocellus not more than 
one-fourth as large as a compound eye 
Vein Sc of fore wing wanting or fea 
AL AS Eo ct a PAC Oa ane By 
ae Sate NE ‘Oligoneuriidae, p. 79 
Vein Sc of fore wing present as a separate 
vein extending from base to apex of 
WE MSN LI ON ir atiac haa ta heat Sesto e 3 
Cubital intercalary veins entirely absent, 
crossveins in disc of fore wing weak and 
Hethke Heady. ss Baetiscidae, p. 75 
Cubital intercalary veins present, cross- 
veins in disc of wing not netlike, figs. 
eee aR tl es oats bv dee ee es + 
Hind tarsus with five clearly differentiated 
segments, true first tarsal segment not 
fused with tibia, figs. 17,19.......... 
2 Ot PAE Heptageniidae, p. 151 
Hind tarsus with only three or four clearly 
differentiated segments, figs. 14-16, 
EB 2 ih a ee a. hack eas 5 
Vein Mz of fore wing sharply bent near 
base, figs. 27, 28, running parallel a 
vein Cu; in this on) NE rg Pe pes OS 
Vein Mb of fore wing straight jena 
its length, figs. 30, 31, 34-37, or curved 
no more than in fig. 29.............. 7. 
Costal crossveins of fore wing in area 
basad of bulla partly or almost com- 
cdg! atrophied; veins M,; and Mp of 
ind wing separating distad of the 
center of wing; fig. 28 
ROT cay Neoephemeridae, p. 42 
Costal crossveins in both fore and hind 
wings well developed; veins M; and Mz 
of hind wing separating proximad of 
center of wing; figs. 27, 38-47........ 
Vib pdinltes a bin dates Ephemeridae, p. 27 
Fore wing with one or two long nas 
veins between Me and Cw, fig. 29. 
Sh ae ea ae Ephemerellidae, p. 55 
Fore wing without long intercalaries be- 
tween veins M2 and Cu, figs. 34-37. 
Vein Cus of fore wing angularly bent 
toward inner wing margin, figs. 35, 
185-192 te. Leptophlebiidae, p. 81 
Vein Cus of fore wing straight or evenly 
curved, figs..31, 34,.36, 37.......... 9 
Cubital intercalary veins of fore wing 
consisting of one or two pairs of long, 
parallel veins, free marginal veinlets 
always absent, fig. 34; hind wings in- 
variably present. Ametropidae, p. 144 
Vol. 26, Art. 1 
Cubital intercalary veins of fore wing 
either a series of short, slightly sinuate 
veins extending from vein Cu; to inner 
wing margin, figs. 36, 37; or cubital in- 
tercalaries one or two long, basally de- 
tached veins accompanied by free 
marginal veinlets, figs. 31, 220-222; 
hind wing sometimes absent....... 
wiles iatle''s. ination eae Baetidae, p. 97 
Mature Nympus 
Gills on abdominal segments 1-6 con- 
cealed under carapace-like projection 
of thoracic notum, fig. 181 
BNE We A ens Shh en Ge Baetiscidae, p. 75 
Abdominal gills not concealed under cara- 
pace-like projection of thoracic notum. 
Second abdominal segment bearing a pair 
of operculate or lidlike gills which cover 
gills on segments 3-6; gills lacking on 
segment 7; figs. 88, 96, 113, 114...... 3 
Second abdominal segment not bearing a 
pair of operculate gills which cover more 
posterior gills; operculate gills, if pres- 
ent, borne by segment 4; gills present on 
segment 7... .2.\...+. s+) 0 oe 4 
Operculate gills fused on meson, connate; 
a hooklike, median spine at posterior 
margin of abdominal tergites 6-8, fig. 
BB hi cat es Neoephemeridae, p. 42 
Operculate gills not fused on meson; ab- 
dominal tergites 6-8 without hooklike 
spines, figs. 96, 113, 1142222 
ere a ete Caenidae, p. 43 
Gills of first abdominal segment large and 
situated on the venter, fig. 184........ 
sons Oe ee: Oligoneuriidae, p. 79 
Gills of first abdominal segment dorsal, or 
first abdominal segment without gills. .5 
Gills always absent from second abdomi- 
nal segment and sometimes absent from 
third segment, also... ...7> ..:eeee 
he ST Ephemerellidae, p. 55 
Gills present on abdominal segments 
Ghia of hind leg shorter than hind tarsal 
claw, figs. 301, 312; or claw at least six 
times as long as wide at its widest point, 
HS e257 ro orca Ametropidae, p. 144 
Tibia of hind leg as long as, or longer than, 
hind tarsal claw, figs. 26, 247, 254, 266, 
385; claws relatively thick. . ei 
Each mandible with a projecting ‘tusk, 
es from dorsal aspect, figs. 2, 55, 
I 8 
Mandibles without projecting tusks... .9 
Gills relatively broad, biramous, with 
margins ciliate, figs. 51-54, 2 
Bie Rae, Oh Ae eng Ephemeridae, p. ay 
Gills slender, filamentous, and bare..... 
Siar party een. Leptophlebiidae, p. 81 
Head flattened dorsoventrally, progna- 
thous, eyes dorsal, and labrum mostly or 
completely concealed under projecting 
anterior margin of head, figs. 360, 383- 
386,:390,, 394, 395... s . 20 cen aneenen eee 
UND eel esas He Heptageniidae, p. 151 
Head hypognathous, eyes lateral, or, if 
prognathous, labrum completely ex- 
