Story by Harvey Thommasen with Photography by Mike Wigle

Mayflies are primitive insects, the order has been in existence for over 200 million years - long before the dinosaurs. All species are aquatic as larvae, and the fragile, terrestrial adults are generally short lived.

Mayflies are unique in that a fully winged terrestrial life stage, known as the subimago,precedes the sexually mature adult stage-the imago.

Four stages; namely, the egg, nymph, subimago (dun), and imago (spinner) comprise the life cycle of the Mayfly. Most species are detrivores and/or herbivores. Mayfly larvae are preferred food for many other aquatic insects, and many fish - including big ones. Mayfly nymphs can be found in almost any kind of freshwater - flowing water, ponds, and in shallow lake areas.

The flyfisher can expect to see at least 25 kinds of mayflies in British Columbia's coastal streams. The species and their common names are listed (Table I). Most people don't bother trying to remember the scientific names, but it is worth keeping a list somewhere so that we are all referring to a specific Mayfly species when we use terms such as March Brown.

MAYFLIES FOUND IN BRITISH COLUMBIA'S COASTAL STREAMS

I. SIPHLONURIDAE

Ameletus validus - Dark Grey Mayfly

II. FAMILY BAETAIDAE

Acentrella turbida - Tiny Western Olive Mayfly

Baetis tricaudatus - Little Blue-wing Olive Mayfly

Baetis bicaudatus - Little Blue-wing Olive Mayfly

Callibaetis nigritus - Calibaetis

III. HEPTAGENIIDAE

Cinygmula uniformis - Small Western Ginger Mayfly

Epeorus (Ironopsis) grandis - Western Quill Gordon

Epeorus (Iron) albertae - Slate-cream Mayfly

Epeorus (Iron) longimanus - Medium Blue Mayfly

Epeorus (Ironodes) nitidus - Little Yellow Mayfly

Rithrogena hageni - Western March Brown

Rithrogena robusta - Western March Brown

IV. LEPTOPHLEBIIDAE

Paraleptophlebia debilis - Slate-winged Mahogany Mayfly

Paraleptophlebia temporalis - Slate-winged Mahogany Mayfly

Paraleptophelbia vaciva - Blue Mayfly

Leptophlebia cupida - Western Black Mayfly

V. EPHEMERELLIDAE

Drunella coloradensis - Small Western Green Drake

Drunella doddsi - Western Green Drake

Drunella flavilinea - Small Western Green Drake

Drunella grandis ingens - Western Green Drake

Drunella spinifera - Small Western Green Drake

Ephemerella inermis - Pale Morning Mayfly

Ephemerella infrequens - Pale Morning Mayfly

Serratella tibialis - Small Western Dark Hendrickson

Mayflies hatches occur from April right through into early November. Each species has its own preferred habitat, preferred time of year to hatch, preferred time of day to hatch. A few species (eg Baetis spp) have several distinct emergences per year.

Preferred Habitat:

Dark Grey Mayfly - Near, but not in, fast water

Tiny Western Olive - Slow to medium fast water

Little Blue-wing Olive - Slow to fast water

Callibaetis - Lakes, ponds, slack stream margins

Cinygma integrum - Fast water

Small Western Ginger - Fast water

Western Quill Gordon - Fast water

Slate-cream Mayfly - Medium to fast water

Medium Blue Mayfly - Fast water in smaller streams

Little Yellow Mayfly - Fast water

Western March Brown - Fast currents

Slate-winged Mahogany - Slower waters adjacent riffles

Blue Mayfly - Slower waters adjacent riffles

Western Black Mayfly - Slow water, occasionally in ponds

Small Western Green Drake - Moderate to fast flowing water

Western Green Drake - Slow to fast flowing water

Pale Morning Mayfly - Slow to fast water

Small Western Dark Hendrickson - Moderate to fast flowing water

Mayfly larvae come in a variety of sizes and colors.

Typical Nymph Coloration Size:

Dark Grey Mayfly - Light brown; purplish brown; 10-14 mm

Tiny Western Olive - Olive brown < 5 mm

Little Blue-wing Olive - Brown to olive brown; 4-8 mm

Callibaetis nigritus - Grayish-brown; 9-12 mm

Cinygma integrum - Dark brown; 10-12 mm

Small Western Ginger - Light to dark brown; 10-12 mm

Western Quill Gordon - Mottled brown; 9-12 mm

Slate-cream Mayfly - Gray brown to gray tan; 9-10 mm

Medium Blue Mayfly - Mottled brown ; 10-11 mm

Little Yellow Mayfly - Dark mottled brown; 9-12 mm

Western March Brown - Olive brown; dark brown; 8-9 mm

Slate-winged Mahogany - Olive brown; dark brown; 6-12 mm

Blue Mayfly - Olive brown; dark brown; 6-12 mm

Western Black Mayfly - Dark chestnut brown; 10-12 mm

Small Western Green Drake - Tan to reddish brown; 12-13 mm

Western Green Drake - Yellow tan to dark brown; 10-14 mm

Pale Morning Mayfly - Dark olive brown to grey; 5- 7 mm

Small Western Dark Hendrickson - Purplish brown

Fortunately, the west coast flyfisher probably does not really need to devise a pattern for each of these Mayfly species. A pattern like the Hares Ear tied in a variety of sizes and shades of brown should work well enough.

The adults, we will hopefully get around to discussing in later columns.