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.

Stream photos

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Isoperla (Stripetails and Yellow Stones) Stonefly Adult Isoperla (Stripetails and Yellow Stones) Stonefly Adult

Dorsal view of a Isoperla (Perlodidae) (Stripetails and Yellow Stones) Stonefly Adult from Mystery Creek #308 in Washington

9 Recently Added Photos

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.

Troutnut is a project started in 2003 by salmonid ecologist Jason "Troutnut" Neuswanger to help anglers and fly tyers unabashedly embrace the entomological side of the sport. Learn more about Troutnut or support the project for an enhanced experience here.

Behavioral Drift - With or Without Case?

This topic is about the Insect Order Trichoptera

Some say caddisflies are even more important than mayflies, and they are probably right. The angling world has taken a while to come to terms with this blasphemy. Caddis imitations are close to receiving their fare share of time on the end of the tippet, but too many anglers still assume all caddisflies are pretty much the same.

Caddis species actually provide as much incentive to learn their specifics as the mayflies do. There is just as much variety in their emergence and egg-laying behaviors, and as many patterns and techniques are needed to match them. Anglers are hampered only by the relative lack of information about caddisfly behavior and identification.

Example specimens

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Female Dicosmoecus gilvipes (October Caddis) Caddisfly Adult

Female Dicosmoecus gilvipes (Limnephilidae) (October Caddis) Caddisfly Adult from the South Fork Snoqualmie River in Washington

I've been hoping to add a really good October Caddis to the photo collection here for years, but so far I had struck out on finding them on the river. Tonight, this one flew into the kitchen during a pizza party at a house along the river, and was quickly pointed out -- one of the perks of hanging out with other aquatic biologists! Maybe next year I can finally get a salmonfly on taco night or something.

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Hydropsyche (Spotted Sedge) Caddisfly Larva

Ventral view of a Hydropsyche (Hydropsychidae) (Spotted Sedge) Caddisfly Larva from the Yakima River in Washington

With a bit of help from the microscope, this specimen keys clearly and unsurprisingly to Hydropsyche.

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Limnephilus (Summer Flier Sedge) Caddisfly Larva

Case view of a Limnephilus (Limnephilidae) (Summer Flier Sedge) Caddisfly Larva from the Yakima River in Washington

DaveC
Posts: 2

DaveC on Jun 18, 2007June 18th, 2007, 9:17 am EDT

The definition provided by Jason suggests that Behavioral Drift occurs when cased larvae simply "let go" of the stream bed, rocks, plants, etc. and drift while still encased within their cases. However, I always presumed the case, or test, was specifically constructed from material that added "ballast" to the grub and therefore prevented it from being swept away in the current.

QUESTION: Do larvae ever crawl OUT of their cases/tests and drift "naked" until they settle somewhere downstream, and then begin to build a NEW case/test?

It would be useful to know whether a "behaviorally drifting caddis" larva pattern should imitate the appearance of a case or test that's constructed of sand, leaves, twigs, etc., or whether it should instead imitate the appearance of just the naked grub.

GONZO
Site Editor
"Bear Swamp," PA

Posts: 1681

GONZO on Jun 18, 2007June 18th, 2007, 9:36 am EDT

Short answer: As I understand it, yes, some behavioral drift of case-building caddisflies is caseless. (Glossosoma and Dicosmoecus larvae are two examples that come to mind. I'm sure there are many others.)

Troutnut

Administrator
Bellevue, WA

Posts: 2758

Troutnut on Jun 18, 2007June 18th, 2007, 9:55 am EDT

Yes, some of them do drift without their cases. Gary LaFontaine in Caddisflies mentions imitating the un-cased drifting larvae of otherwise case-building caddisflies in at least a few places.

Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist

JeffK
Hackettstown NJ

Posts: 1

JeffK on Jul 3, 2007July 3rd, 2007, 8:49 am EDT

One October on the Beaverkill the rocks were covered with a sand cased caddis. When I tried to catch them they scooted away and I couldn't catch them by hand. I was surprised that cased caddis could be so frisky. The cased caddis I see in the spring are easy to catch by hand.