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.

Sunlight perfectly strikes the trees at a bend in the Foss River in the Washington Cascades.

From the Foss River in Washington

Stream photos

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Holocentropus Caddisfly Larva Holocentropus Caddisfly Larva

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.

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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.

Which aquatic insects are most vulnerable to pollution???

Byhaugh
Hawaii

Posts: 56

Byhaugh on Aug 13, 2014August 13th, 2014, 1:28 pm EDT

Stoneflies?
Mayflies?
Or Caddisflies

PaulRoberts

Colorado

Posts: 1776

PaulRoberts on Aug 13, 2014August 13th, 2014, 3:55 pm EDT

Depends on species and type of pollution. There are species within each that are adapted to somewhat reduced oxygen levels (a common result of organic and physical pollution). Of the three, I think there are few if any stoneflies that are adapted to warmer, lower O2 waters.

What is your interest? School project?

Catskilljon
Upstate NY

Posts: 160

Catskilljon on Aug 13, 2014August 13th, 2014, 6:50 pm EDT

If I had to make an assumption based on what I have seen, its stonefly, mayfly and caddis in that order going from cleanest to polluted. There are a few streams in NJ that don't have stoneflies, have a few mayflies but are loaded with caddis, and these are streams running through and around semi-populated housing and business districts.

When I see stonefly shucks on the rocks of a new stream I have never fished...it makes me smile. They are the live canary in the cold mine. CJ

Crepuscular

Boiling Springs, PA

Posts: 920

Crepuscular on Aug 14, 2014August 14th, 2014, 7:27 am EDT

Depends on species and type of pollution. There are species within each that are adapted to somewhat reduced oxygen levels (a common result of organic and physical pollution). Of the three, I think there are few if any stoneflies that are adapted to warmer, lower O2 waters.

What is your interest? School project?

Byhaugh, It's tough to make generalizations about that topic. It's not that simple. Google Hilsenhoff tolerance values and that will get you started. Like Paul pointed out it depends upon what type of pollution you are taking about. For example, some stonefly genera can take a much lower pH than other stoneflies. Depending upon the specific type of pollution, there may be certain genera of a particular insect order present but others will not be there. So the point I suppose I'm trying to make is that to generalize on the order level of classification may not really be that meaningful.

Lastchance
Portage, PA

Posts: 437

Lastchance on Aug 14, 2014August 14th, 2014, 1:12 pm EDT

sulfurs