An Introduction to Mayflies
Anglers will see mayflies flittering gracefully around the sky from March through November when conditions are right for emergence. Cold, clean water is necessary for mayflies (Ephemeroptera) to flourish and the Montana rivers near Bozeman are flush with mayfly hatches. Angling success often hinges on an anglers' ability to identify the insect species and understand the mayfly lifecycle.
Characteristics of Mayflies
- Transparent wings carrying them through the air and stand tall like sailboats when still. Males are the gender commonly seen swarming over the surface of the water before a spinner fall.
- 3 long tails create an ‘M’, which helps in remembering this common-occurring food source for trout all over Montana. (some species have 2 tails, so don’t rely solely on this morphologic indicator for identification)
- Mayfly colors can vary from gray, brown, olive, tan, yellow, and green. They also come in a variety of sizes ranging from hook size #10-#18 or even #20.
Overview of the Mayfly Lifecycle
- Female mayflies lay eggs in or on freshwater by dipping their abdomen below the surface during flight. They then grow to nymphs in a matter of days or sometimes weeks, which have gills and can be seen crawling on the underside of river stones year-round.
- They feed on algae and other plant detritus, and if well fed, can produce up to 3 generations per year. Some species take up to 3 years to mature.
- When they emerge, they rise to the surface and break free from the nymph stage and fly weakly. Unlike any other insect, they still need to molt one more time before they can fly properly and reproduce.
Montana Fly Fishing Mayfly Hatches of Note
- Blue-winged olives, pale morning duns, green drakes, brown drakes, tricos, Callibaetis, and March brown mayfly hatches are the most significant mayfly hatches to anglers fly fishing in Montana.
- Mayfly hatch activity is prevalent throughout our Montana fly fishing guide trip season, lasting from March through October.
Top 10 Mayfly Dry Fly Patterns for Fly Fishing in Montana
