Common Names: Hex, big yellow mayfly, giant mayfly
Scientific Name: Hexagenia limbata

Among the largest of American mayflies, Hexagenia limbata inhabits some lakes and slow sections of a few rivers. Hatches usually start between May and early July, depending on the local climate; I've seen them hatch in May on the Oregon coast, mid-June in California, and July in the Cascade mountains. The hatch season can last anywhere from three weeks to two months.

Because the nymphs burrow into silty bottoms and only come out to feed at night, it makes no sense to fish a nymph imitation until the hatch season, and even then you need to restrain yourself until near dusk because the hatch doesn't start until the sun kisses the horizon.

An hour or two before the hatch starts, go to water that is less than ten-feet deep. Use a weighted fly or lead on the leader, and let the your nymph settle to the bottom. Pull it up two or three feet, pause, then let it settle back down; repeat this several times before casting again. Sometimes this takes a trout, but mostly it gives you something to do while you're waiting for the actual hatch.

Hatches begin just before sunset, so take a flashlight with you. When you see duns on the surface, forget the nymph and tie on a dry. Cripple imitations can be especially productive during the hatch. Occasionally impart some action to the fly; the naturals can be quite active.

Spinners are not important to anglers.


How to Match a Hexagenia

Hatches are matched from Westfly's database of "standard" fly patterns.

Size 8-10 Burks Hexagenia. Yellow body and wing
Size 8-10 Quigley Cripple. Yellow body and wing
Slow water, lakes: standard dry fly, chuck-and-sit
Size 8-10 Hexagenia Parachute. Yellow body and wing
Slow water, lakes: standard dry fly, chuck-and-sit


NYMPH COLOR: yellow-brown

DUN SIZE: 16-35 mm (5/8 to 1-3/8 in)

DUN COLOR: Wings--yellow. Body--yellow or light tan; the underside is solid, but the top can have dark marks on the abdominal segments.

OTHER CHARACTERISTICS: Nymph--large tusks. Dun--two tails.