Mayfly

An Identification guide to the Nymphal Mayflies
(Order EPHEMEROPTERA) of British Columbia

	FAMILY METRETOPODIDAE
TAXONOMIC CHARACTERS	Mandibles rarely with tusks; foreleg tarsal claw forked, different in structure from mid- and hindleg claws; all legs with tarsi longer than tibiae; gills on abdominal segment 2 present; paired dorsal tubercles on abdominal segments rarely present; head and body not distinctly flattened dorso-ventrally
DISTRIBUTION IN NORTH AMERICA	Alaska; Canada; Central, Northeastern, and Southeastern U.S.A.
TOTAL NUMBER OF GENERA IN N.A.	2
TOTAL NUMBER OF GENERA IN B.C.	1
TOTAL NUMBER OF SPECIES IN N.A.	8
TOTAL NUMBER OF SPECIES IN B.C.	1

GENUS METRETOPUS

TAXONOMIC
CHARACTERS

Foreleg tarsal claws edged with spines; gills on all abdominal segments single; gills on abdominal segment 4 with several spines along outer edge

HABITAT

Among vegetation of slow-moving streams

HABIT

Swimming or clinging

FEEDING METHOD

Unknown

COMMENTS

Extremely rare

SPECIES RECORDED
IN B.C. TO DATE

borealis

Figure 13. Family Siphlonuridae - Parameletus columbiae nymph

FAMILY SIPHLONURIDAE

TAXONOMIC
CHARACTERS

Labrum without a distinct notch in the midline; mandibles rarely with tusks; maxilla without a fringed bottom edge; antennae short; tarsal claws on all legs similar in structure; abdominal gills not forked, may be doubled, but never ending in a slender process; gills on abdominal segment 2 present; paired dorsal tubercles on abdominal segments rarely present; head and body not distinctly flattened dorso-ventrally

DISTRIBUTION IN
NORTH AMERICA

Widespread

TOTAL NUMBER OF
GENERA IN N.A.

4

TOTAL NUMBER OF
GENERA IN B.C.

2

TOTAL NUMBER OF
SPECIES IN N.A.

25

TOTAL NUMBER OF
SPECIES IN B.C.

4

GENUS PARAMELETUS

TAXONOMIC
CHARACTERS

Labial palps with pincer-like ends; gills on abdominal segments 1 and 2 with single lamellae; abdominal segments with prominent posterolateral projections

HABITAT

Quiet waters of swamps and forest pools

HABIT

Swimming or climbing

FEEDING METHOD

Unknown

COMMENTS

Uncommon

SPECIES RECORDED
IN B.C. TO DATE

columbiae

GENUS SIPHLONURUS

TAXONOMIC
CHARACTERS

Gills on abdominal segments 1 and 2 with double lamellae; abdominal segments with prominent posterolateral projections

HABITAT

Among vegetation in quiet areas of ponds or streams

HABIT

Swimming or climbing

FEEDING METHOD

Collecting-gathering, scraping, shredding, or predation

COMMENTS

Some species can be found in small, stagnant pools

SPECIES RECORDED
IN B.C. TO DATE

autumnalis, columbianus, occidentalis

Figure 14. Family Tricorythidae - Tricorythodes sp. nymph

FAMILY TRICORYTHIDAE

TAXONOMIC
CHARACTERS

Mandibles rarely with tusks; gills on abdominal segment 2 covering or partially covering succeeding pairs of gills, but not meeting in the midline; gills on abdominal segments 3-6 without fringed edges and simple or bilobed

DISTRIBUTION IN
NORTH AMERICA

Widespread

TOTAL NUMBER OF
GENERA IN N.A.

2

TOTAL NUMBER OF
GENERA IN B.C.

1

TOTAL NUMBER OF
SPECIES IN N.A.

24

TOTAL NUMBER OF
SPECIES IN B.C.

1

GENUS TRICORYTHODES

TAXONOMIC
CHARACTERS

Hind wing pads absent in mature nymphs; fore femur with a transverse band of long hairs; tarsal claws long, with hooked ends

HABITAT

Silted areas of streams and rivers

HABIT

Sprawling or clinging

FEEDING METHOD

Collecting-gathering

COMMENTS

Massive swarms common

SPECIES RECORDED
IN B.C. TO DATE

minutus

	GENUS METRETOPUS
TAXONOMIC CHARACTERS	Foreleg tarsal claws edged with spines; gills on all abdominal segments single; gills on abdominal segment 4 with several spines along outer edge
HABITAT	Among vegetation of slow-moving streams
HABIT	Swimming or clinging
FEEDING METHOD	Unknown
COMMENTS	Extremely rare
SPECIES RECORDED IN B.C. TO DATE	borealis

	FAMILY SIPHLONURIDAE
TAXONOMIC CHARACTERS	Labrum without a distinct notch in the midline; mandibles rarely with tusks; maxilla without a fringed bottom edge; antennae short; tarsal claws on all legs similar in structure; abdominal gills not forked, may be doubled, but never ending in a slender process; gills on abdominal segment 2 present; paired dorsal tubercles on abdominal segments rarely present; head and body not distinctly flattened dorso-ventrally
DISTRIBUTION IN NORTH AMERICA	Widespread
TOTAL NUMBER OF GENERA IN N.A.	4
TOTAL NUMBER OF GENERA IN B.C.	2
TOTAL NUMBER OF SPECIES IN N.A.	25
TOTAL NUMBER OF SPECIES IN B.C.	4

	GENUS PARAMELETUS
TAXONOMIC CHARACTERS	Labial palps with pincer-like ends; gills on abdominal segments 1 and 2 with single lamellae; abdominal segments with prominent posterolateral projections
HABITAT	Quiet waters of swamps and forest pools
HABIT	Swimming or climbing
FEEDING METHOD	Unknown
COMMENTS	Uncommon
SPECIES RECORDED IN B.C. TO DATE	columbiae

	GENUS SIPHLONURUS
TAXONOMIC CHARACTERS	Gills on abdominal segments 1 and 2 with double lamellae; abdominal segments with prominent posterolateral projections
HABITAT	Among vegetation in quiet areas of ponds or streams
HABIT	Swimming or climbing
FEEDING METHOD	Collecting-gathering, scraping, shredding, or predation
COMMENTS	Some species can be found in small, stagnant pools
SPECIES RECORDED IN B.C. TO DATE	autumnalis, columbianus, occidentalis

	FAMILY TRICORYTHIDAE
TAXONOMIC CHARACTERS	Mandibles rarely with tusks; gills on abdominal segment 2 covering or partially covering succeeding pairs of gills, but not meeting in the midline; gills on abdominal segments 3-6 without fringed edges and simple or bilobed
DISTRIBUTION IN NORTH AMERICA	Widespread
TOTAL NUMBER OF GENERA IN N.A.	2
TOTAL NUMBER OF GENERA IN B.C.	1
TOTAL NUMBER OF SPECIES IN N.A.	24
TOTAL NUMBER OF SPECIES IN B.C.	1

	GENUS TRICORYTHODES
TAXONOMIC CHARACTERS	Hind wing pads absent in mature nymphs; fore femur with a transverse band of long hairs; tarsal claws long, with hooked ends
HABITAT	Silted areas of streams and rivers
HABIT	Sprawling or clinging
FEEDING METHOD	Collecting-gathering
COMMENTS	Massive swarms common
SPECIES RECORDED IN B.C. TO DATE	minutus