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Hex Mayflies
Hexagenia limbata

The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large Brown Trout that only touch streamers for the rest of the year.

Updates from March 21, 2011

Closeup insects by Entoman from the Lower Yuba River in California

Ephemerella dorothea infrequens (Pale Morning Dun) Mayfly Nymph
Habitat: Shallow riffle over cobble; approx. 1 ft. deep
Size: 8.5 mm. Mature specimens have been captured as large as 10.5 mm.
Emergence schedule: Variable - starting as early as mid March and lasting as late as early June, depending on the year. Usual duration is at least several weeks or more.
Dun Association: Body is elusive pale creamy yellow w/ orange highlights, cream legs and tails, and dun wings
Specimen status in photo: Preserved
Collection method: Kick net

Comments: Extremely common in samples taken from this location. It's color in life was very close to as depicted in the photo; except for the gradual darkening of the abdominal segments as they progress posteriorly, which has been accentuated somewhat by the effects of preservation. Adult association is based upon capture of this taxon at various stages of emergence including: darkened wingcases, split thoraxic notums, and partially ecloded or ''stillborn'' specimens.

Entoman
Isoperla quinquepunctata (Little Yellow Stonefly) Stonefly Nymph
Size - (excluding tails) - 10 mm
Status at time of photo - preserved but no discernible color change as specimen was captured only a few days earlier.
Key characters - unique pattern on dorsal head and thorax; dark medial terga stripe between two paler stripes

This species is very common in west slope north Sierra watersheds. Richard W. Baumann & Boris C. Kondratieff did a study on the same section and at the same time of year (APRIL 25-29, 2010) where this specimen was taken. No other species of Isoperla were reported from this location and quinquepunctata was very abundant. Their hatches can be very heavy some Springs.

Entoman
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