**Mayfly Genus Procloeon (Blue-Winged Olives)**

Mayflies

Caddisflies

Stoneflies

Taxonomic Navigation -?-

Kingdom Animalia (Animals)

» Phylum Arthropoda (Arthropods)

» Class Insecta (Insects)

» Order Ephemeroptera (Mayflies)

» Family Baetidae (Blue-Winged Olives)

» Genus Procloeon (Blue-Winged Olives)

Species in Procloeon
Procloeon ingensBlue-Winged Olive	0	0
Procloeon insignificansBlue-Winged Olive	0	0
Procloeon mendaxBlue-Winged Olive	0	0
Procloeon rubropictumBlue-Winged Olive	0	0
Procloeon rufostrigatumBlue-Winged Olive	0	0
Procloeon simplexBlue-Winged Olive	0	0

16 species aren't included.

Common Names

Match	Common Name
	Blue-Winged Olives
	Gray-Winged Olive Quills
	Tiny Sulphur Duns

Fly Imitations by Orvis

Stage	Fly Pattern
Dun	Blue Winged Olive

This genus is not well-known to fly fishers yet because most of its species were, until very recently, classified as either Centroptilum or Cloeon.

These mayflies may be abundant enough to cause fishable hatches in spite of their tiny size.

It's difficult to discern from previous angling literature exactly which statements now apply to Procloeon, because its species come from other little-known genera and the accounts for them conflict. They were mentioned in combination with other genera, adding to the confusion. So the information below is highly tentative and, where accounts seem to conflict, both have been given.

Where & When

Time Of Year (?): Mostly summer
Preferred Waters: Best in alkaline (Alkaline: Having a pH higher than 7 (opposite of acidic). Moderately alkaline water is ideal for trout because it's better for the growth of phytoplankton, the usual base of the aquatic food chain, and that's good for the growth of everything higher up the chain, including trout.) streams

Hatching Behavior

Time Of Day (?): Different sources say mid-evening or early morning

Trout may feed well on the tiny nymphs during a hatch. Caucci and Nastasi discovered and noted in Hatches II that these nymphs, despite their excellent swimming ability most of the time, become nearly immobile shortly before hatching. They slowly crawl out of the water or dead-drift (Dead-drift: The manner in which a fly drifts on the water when not moving by itself or by the influence of a line. Trout often prefer dead-drifting prey and imitating the dead-drift in tricky currents is a major challenge of fly fishing.) float to the surface, buoyed by gases they release.

According to one source, the duns crawl out onto shore to emerge.

Spinner Behavior

Procloeon duns usually molt into spinners, mate, and die the very day they hatched. Dun and spinner activity may overlap.

Nymph Biology

Current Speed: Slow
Substrate: Many, but weeds are best

They either prefer fertile, weedy spring creeks, or slow, silty stretches of relatively warm trout rivers, depending on which books should be believed.

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Jargon Defined:

Alkaline: Having a pH higher than 7 (opposite of acidic). Moderately alkaline water is ideal for trout because it's better for the growth of phytoplankton, the usual base of the aquatic food chain, and that's good for the growth of everything higher up the chain, including trout.

Dead-drift: The manner in which a fly drifts on the water when not moving by itself or by the influence of a line. Trout often prefer dead-drifting prey and imitating the dead-drift in tricky currents is a major challenge of fly fishing.

Duns: Mayflies have two adult stages. They first emerge from the water as duns (scientifically known as the subimago stage). They then molt into the spinner (imago) stage, in which they mate and die. Sometimes the word "dun" is confusingly used to refer to a brownish gray color in fly tying materials.

Molt: When aquatic insects with hard exoskeletons (like mayfly and stonefly nymphs) grow bigger, their exoskeleton does not grow with them. Instead they grow a new, larger one underneath and shed the old one when it's too small. This process is called molting.

Nymphs: The juvenile, underwater stages of mayflies, stoneflies, dragonflies, and damselflies and other aquatic insects whose juvenile stages are covered by hard exoskeletons. The word can also refer to the fishing flies which imitate these creatures, in which case it is used as a blanket term for flies imitating any underwater stage of an invertebrate (except for crayfish and leeches).

Spinner: There are two winged stages of adult mayflies. They emerge from the water as duns, molt on land (usually) into their fully mature stage, spinners. As spinners, they mate, lay eggs, and die.

Useful References:

Caucci, Al and Nastasi, Bob. 2004. Hatches II. The Lyons Press.

Knopp, Malcolm and Robert Cormier. 1997. Mayflies: An Angler's Study of Trout Water Ephemeroptera . The Lyons Press.

Schwiebert, Ernest G. 1955. Matching the Hatch. MacMillan Publishing Company.