276 BULLETIN OF THE BUREAU OF FISHERIES. 
Foop or NINE SPECIMENS OF RIVER HERRING (POMOLOBUS CHRYSOCHLORIS). 
Hexagenia 
Pentage- - 
No. Date. Locality. Collector. nia Adults Hepta- Miscella- 
nymphs. x He = Es genia. | neous. 
ymPAS-! subima- ges 
gos.2 
1 | May 23,1916 
2| June 4,1915 
3 | June 11,1916 
4) June 21,1915 
5 | July 2, 1916 : 
6| July 4,1915 |..... GAT. ee tadssas ae Stringham. veeteees| Many. Many. c 
7 | July 14,1916 | Lake Cooper above depot..|.....do... I I 209 c 
By) Ree MOS PACTS, Dear -beeit oes eae AUOW SIE? S215 duc halen 3 Too c 
9) |: Sept, 8; xox6|, Keokuk, above darn sci o22| ccc sis wicisr teeiein|pciislan eae] Seoetetere matte J 100 c) 
@ Approximate only; many badly disintegrated. 
b The fishes named below were not sent me, having been previously determined. 
¢ Occurring in large numbers. 
@ A damselfly nymph of the genus Argia. 
€ x Hiodon and 4 undetermined fishes. 
/ 2 Hiodon, 4 Dorosoma, 10 undetermined fishes. 
9 Of recognizable specimens all were females. 
h 20 caddisflies of the family Leptoceridz. 
Evidently, during the season of flight of Hexagenia, this fish gorges itself with 
adults. Earlier it eats the nymphs. The eggs found might about equally well be 
obtained from nymph or adult, since they are matured, so far as external aspect is con- 
cerned, during the nymphal period. 
SYSTEMATIC ACCOUNT OF THE GROUP. 
The burrowing mayflies and their allies comprising the subfamily Ephemerine 
include in North America half a dozen genera of rather large species. Among these 
are the largest of our mayflies, the ‘‘brown drakes”’ of the genus Hexagenia, which by 
reason of their enormous swarms are known to everyone; the ‘‘yellow drakes”’ of the 
genus Pentagenia; the beautiful ‘“‘mackerels” of the genus Ephemera, with ornate color 
patterns on both wings and body, and most graceful and lively nuptial flight; and 
several genera of smaller and less familiar mayflies. These will be characterized and 
illustrated and an account of their habits so far as known will be given in the following 
pages. 
The group of the burrowing mayflies may be distinguished from other groups, and 
the genera of the group may be distinguished from each other in both adult and larval 
stages as follows: 
KEY TO THE SUBFAMILIES OF EPHEMERIDA. 
A. Adults. 
1. Basal fork of the cubital vein 4 strongly unilateral; cubital and first anal veins strongly divergent 
EY La Sea OR a OCR Ean Sonia Sune ane Berne fe RRS ANS neko s gaat Boe Romolo EPHEMERINA. 
Basal fork of the cubital vein symmetrical, or nearly so; cubital and first anal veins at base parallel 
OPsveby slightly: cuverpentts: a crem er ier ceo) sate ntfs len eet 6 Batina: and HEPTAGENINA. 
B. Nymphs. 
1. Mandibles with a prominent, tusklike, external branch projecting forward from the mouth and 
‘visible from abovert,. oo. ASEESa a aor ee SSE GOCE: opate[etiets «a ar- ARE soya EPHEMERINA. 
Mandibles not; “tusked 7-5 ecse ari erie i eee cre lotr ieteda inte sta crete +b BaHTIna and HEPTAGENINA. 
@ The terminology of the venation of the wings is illustrated and explained in Plate LXXXI, figure ss. 
> Not here treated. 
