Mayfly

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

	GENUS CALLIBAETIS
TAXONOMIC CHARACTERS	Hind wing pads present in mature nymphs; tarsal claws with a double row of tiny denticles; gills on one or more abdominal segments with large flaps; caudal filaments without dark bands every 3rd, 4th, or 5th segment
HABITAT	Among vegetation or on the bottom of still waters
HABIT	Swimming or clinging
FEEDING METHOD	Collecting-gathering
COMMENTS	Tolerant of a wide range of water temperatures and acidities
SPECIES RECORDED IN B.C. TO DATE	americanus

GENUS CENTROPTILUM

TAXONOMIC
CHARACTERS

Tarsal claws shorter than length of tarsi; gills on all abdominal segments simple; caudal filaments with dark bands every 3rd, 4th, or 5th segment; apices of caudal filaments without lateral bristles

HABITAT

On sandy bottoms of slow or quiet waters

HABIT

Swimming or clinging

FEEDING METHOD

Collecting-gathering or scraping

COMMENTS

Many species now placed in Procloeon

SPECIES RECORDED
IN B.C. TO DATE

bifurcatum

GENUS DIPHETOR

TAXONOMIC
CHARACTERS

Villopore absent; gills absent from abdominal segment 1; gills on abdominal segments 2-7 simple; caudal filaments without dark bands every 3rd, 4th, or 5th segment

HABITAT

Among vegetation of shallow, flowing waters

HABIT

Swimming or clinging

FEEDING METHOD

Unknown

COMMENTS

One species, D. hageni, is obligately parthenogenetic

SPECIES RECORDED
IN B.C. TO DATE

hageni

GENUS PROCLOEON

TAXONOMIC
CHARACTERS

Tarsal claws shorter than length of tarsi; gills on all abdominal segments simple, although gills on abdominal segment 1 may have a dorsal flap; caudal filaments with dark bands every 3rd, 4th, or 5th segment; apices of caudal filaments with lateral bristles

HABITAT

Among vegetation of slow-flowing streams, lakes, or ponds

HABIT

Swimming or clinging

FEEDING METHOD

Collecting-gathering or scraping

COMMENTS

Many species formerly placed in Cloeon or Centroptilum

SPECIES RECORDED
IN B.C. TO DATE

album, bellum, conturbatum, implicatum

Figure 8. Family Caenidae - Caenis sp. nymph

FAMILY CAENIDAE

TAXONOMIC
CHARACTERS

Mandibles rarely with tusks; hind wing pads absent in mature nymphs; gills on abdominal segment 2 covering or partially covering succeeding pairs of gills and meeting or almost meeting in the midline, but never fused; gills on abdominal segments 3-6 with fringed edges

DISTRIBUTION IN
NORTH AMERICA

Widespread

TOTAL NUMBER OF
GENERA IN N.A.

4

TOTAL NUMBER OF
GENERA IN B.C.

1

TOTAL NUMBER OF
SPECIES IN N.A.

26

TOTAL NUMBER OF
SPECIES IN B.C.

1

GENUS CAENIS

TAXONOMIC
CHARACTERS

Labial palps and maxillary palps three-segmented; fore tibia and tarsus edged with a row of spines; gills on abdominal segment 2 with fringed edges; middle abdominal segments with prominent posterolateral projections

HABITAT

Among debris or vegetation of slow-moving or stagnant waters

HABIT

Sprawling or climbing

FEEDING METHOD

Collecting-gathering or scraping

COMMENTS

Some species pollution-tolerant; some species positively phototactic

SPECIES RECORDED
IN B.C. TO DATE

simulans

Figure 9. Family Ephemerellidae - Serratella sp. nymph

FAMILY EPHEMERELLIDAE

TAXONOMIC
CHARACTERS

Mandibles rarely with tusks; gills on abdominal segment 1 rudimentary or absent; gills on abdominal segment 2 absent; gills on abdominal segment 3 present or absent; abdominal gills with double lamellae; paired dorsal tubercles on abdominal segments often present

DISTRIBUTION IN
NORTH AMERICA

Widespread

TOTAL NUMBER OF
GENERA IN N.A.

8

TOTAL NUMBER OF
GENERA IN B.C.

7

TOTAL NUMBER OF
SPECIES IN N.A.

90

TOTAL NUMBER OF
SPECIES IN B.C.

18

	GENUS CENTROPTILUM
TAXONOMIC CHARACTERS	Tarsal claws shorter than length of tarsi; gills on all abdominal segments simple; caudal filaments with dark bands every 3rd, 4th, or 5th segment; apices of caudal filaments without lateral bristles
HABITAT	On sandy bottoms of slow or quiet waters
HABIT	Swimming or clinging
FEEDING METHOD	Collecting-gathering or scraping
COMMENTS	Many species now placed in Procloeon
SPECIES RECORDED IN B.C. TO DATE	bifurcatum

	GENUS DIPHETOR
TAXONOMIC CHARACTERS	Villopore absent; gills absent from abdominal segment 1; gills on abdominal segments 2-7 simple; caudal filaments without dark bands every 3rd, 4th, or 5th segment
HABITAT	Among vegetation of shallow, flowing waters
HABIT	Swimming or clinging
FEEDING METHOD	Unknown
COMMENTS	One species, D. hageni, is obligately parthenogenetic
SPECIES RECORDED IN B.C. TO DATE	hageni

	GENUS PROCLOEON
TAXONOMIC CHARACTERS	Tarsal claws shorter than length of tarsi; gills on all abdominal segments simple, although gills on abdominal segment 1 may have a dorsal flap; caudal filaments with dark bands every 3rd, 4th, or 5th segment; apices of caudal filaments with lateral bristles
HABITAT	Among vegetation of slow-flowing streams, lakes, or ponds
HABIT	Swimming or clinging
FEEDING METHOD	Collecting-gathering or scraping
COMMENTS	Many species formerly placed in Cloeon or Centroptilum
SPECIES RECORDED IN B.C. TO DATE	album, bellum, conturbatum, implicatum

	FAMILY CAENIDAE
TAXONOMIC CHARACTERS	Mandibles rarely with tusks; hind wing pads absent in mature nymphs; gills on abdominal segment 2 covering or partially covering succeeding pairs of gills and meeting or almost meeting in the midline, but never fused; gills on abdominal segments 3-6 with fringed edges
DISTRIBUTION IN NORTH AMERICA	Widespread
TOTAL NUMBER OF GENERA IN N.A.	4
TOTAL NUMBER OF GENERA IN B.C.	1
TOTAL NUMBER OF SPECIES IN N.A.	26
TOTAL NUMBER OF SPECIES IN B.C.	1

	GENUS CAENIS
TAXONOMIC CHARACTERS	Labial palps and maxillary palps three-segmented; fore tibia and tarsus edged with a row of spines; gills on abdominal segment 2 with fringed edges; middle abdominal segments with prominent posterolateral projections
HABITAT	Among debris or vegetation of slow-moving or stagnant waters
HABIT	Sprawling or climbing
FEEDING METHOD	Collecting-gathering or scraping
COMMENTS	Some species pollution-tolerant; some species positively phototactic
SPECIES RECORDED IN B.C. TO DATE	simulans

	FAMILY EPHEMERELLIDAE
TAXONOMIC CHARACTERS	Mandibles rarely with tusks; gills on abdominal segment 1 rudimentary or absent; gills on abdominal segment 2 absent; gills on abdominal segment 3 present or absent; abdominal gills with double lamellae; paired dorsal tubercles on abdominal segments often present
DISTRIBUTION IN NORTH AMERICA	Widespread
TOTAL NUMBER OF GENERA IN N.A.	8
TOTAL NUMBER OF GENERA IN B.C.	7
TOTAL NUMBER OF SPECIES IN N.A.	90
TOTAL NUMBER OF SPECIES IN B.C.	18