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Lateral view of a Male Baetis (Baetidae) (Blue-Winged Olive) Mayfly Dun from Mystery Creek #43 in New York
Blue-winged Olives
Baetis

Tiny Baetis mayflies are perhaps the most commonly encountered and imitated by anglers on all American trout streams due to their great abundance, widespread distribution, and trout-friendly emergence habits.

Dorsal view of a Holocentropus (Polycentropodidae) Caddisfly Larva from the Yakima River in Washington
This one seems to tentatively key to Holocentropus, although I can't make out the anal spines in Couplet 7 of the Key to Genera of Polycentropodidae Larvae nor the dark bands in Couplet 4 of the Key to Genera of Polycentropodidae Larvae, making me wonder if I went wrong somewhere in keying it out. I don't see where that could have happened, though. It might also be that it's a very immature larva and doesn't possess all the identifying characteristics in the key yet. If Holocentropus is correct, then Holocentropus flavus and Holocentropus interruptus are the two likely possibilities based on range, but I was not able to find a description of their larvae.
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

References

  • Caucci, Al and Nastasi, Bob. 2004. Hatches II. The Lyons Press.
  • LaFontaine, Gary. 1981. Caddisflies. The Lyons Press.
  • Swisher, Doug and Carl Richards. 2000. Selective Trout. The Lyons Press.

Caddisfly Family Hydroptilidae (Microcaddisflies)

Taxonomy
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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