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Lateral view of a Female Hexagenia limbata (Ephemeridae) (Hex) Mayfly Dun from the Namekagon River in Wisconsin
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.

Dorsal view of a Zapada cinctipes (Nemouridae) (Tiny Winter Black) Stonefly Nymph from the Yakima River in Washington
Nymphs of this species were fairly common in late-winter kick net samples from the upper Yakima River. Although I could not find a key to species of Zapada nymphs, a revision of the Nemouridae family by Baumann (1975) includes the following helpful sentence: "2 cervical gills on each side of midline, 1 arising inside and 1 outside of lateral cervical sclerites, usually single and elongate, sometimes constricted but with 3 or 4 branches arising beyond gill base in Zapada cinctipes." This specimen clearly has the branches and is within the range of that species.
27" brown trout, my largest ever. It was the sub-dominant fish in its pool. After this, I hooked the bigger one, but I couldn't land it.
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Caddisfly Family Hydroptilidae (Microcaddisflies)

Both anglers and entomologists know these diminutive flies as "Microcaddisflies." The term refers to this family specifically, not to all tiny caddisflies. Many are large enough for imitation on small hooks, but some are impossibly small, as tiny as hook size 36.

Like the Tricorythodes mayflies, Microcaddisflies can be important to trout because of their extreme abundance in certian waters.

Where & when

In 2375 records from GBIF, adults of this family have mostly been collected during June (29%), July (27%), August (18%), May (12%), and September (7%).

In 755 records from GBIF, this family has been collected at elevations ranging from 3 to 10177 ft, with an average (median) of 1713 ft.

Family Range

Hatching behavior

Pupae emerge on the surface, where they struggle for a long time to break through.

Egg-Laying behavior

Females dive to the bottom to lay their eggs.

Larva & pupa biology

Diet: Plankton or algae (including filamentous)

Shelter type: Plant matter, rock, sand, or silk

Hydroptilidae larvae don't build cases until their fifth and last instar, although they do speed through the first four instars in the first two weeks of their lives. In the fifth instar, their abdomens grow proportionally huge and they build flat cases from a variety of materials. Leucotrichia pictipes, for example, builds oval silk cases which at first are not recognizable as caddis cases at all to anyone not familiar with the species.

Specimens of the Caddisfly Family Hydroptilidae

1 Male Adult
1 Adult
1 Larva

2 Underwater Pictures of Hydroptilidae Caddisflies:

Discussions of Hydroptilidae

Tiny Black Caddis hatch, late fall - Nov 26 to be exact_ Spring Creek Southern MO
21 replies
Posted by Dai_sca on Dec 29, 2010
Last reply on Dec 10, 2019 by Pdcox
I had not fished Bennett Spring for many years and ended up there on Nov 26. I was not very prepared for the stream's entemology, spoke to someone at the flyshop and went with fishing a midge or two and this was very successful. But it was quite obvious that the trout were feeding on the surface or just under and it wasn't a midge. As the day progressed and late afternoon brought sunshine, a hatch of Tiny Caddis(Black) appeared. I had a size 18 but it wasn't dark enough or small enough. A gent who fished the stream regularly gave me a #24 black Elk Hair(or other hair) caddis. The fish took this fly as a dry off the surface. I am hard pressed to ID this fly aside from Protoptila. This, however, is not a marginally temp spring, the water is consistent flow a cold. The description of the Protoptila indicates that this insect is more a warm water insect. The hatch was occurring right at the spring itself. Any ideas?

Again, this was a size 24 fly, and maybe,just maybe, a 26 or 28 might have been the appropriate size for the insect as there were obvious refusals at the surface.

David (dai_sca@yahoo.com

Start a Discussion of Hydroptilidae


Caddisfly Family Hydroptilidae (Microcaddisflies)

12 genera (Alisotrichia, Ithytrichia, Mayatrichia, Metrichia, Neotrichia, Nothotrichia, Ochrotrichia, Orthotrichia, Paucicalcaria, Rioptila, Stactobiella, and Zumatrichia) aren't included.
Family Range
Common Name
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