Notes on Aquatic Entomology

Prepared By: Steve La Falce

One acre of trout stream bottom can produce 100 pounds of nymphs and larvae, the favorite food for trout. A really productive stream can produce 200 pounds per bottom acre!

Insects that trout eat spend all but a few days of their lives under water. The Mayflies, Stoneflies and Caddis flies are totally aquatic Mayflies and stoneflies in the immature stages of life are called NYMPHS while caddis flies are properly called LARVAE but fisherman call them nymphs as well.

Caddis flies (some 1200 species in North America) have a COMPLETE life cycle consisting of stages called egg, larva, pupa and adult.

Mayflies (700 species in NA) and stoneflies (close relatives of cockroaches, 500 species in NA) have what is called an INCOMPLETE life cycle of stages called egg, nymph and adult. The nymph has a HEAD, with “feelers” and eyes, a THORAX with six legs and developing wing cases, an ABDOMEN consisting of several segments, and two or three tails, depending on the species.

When the mayflies and stoneflies “hatch”, that is, turn into adult (called sub-imago) insects, the wing cases split open and the adult emerges from the “shell”.

Trout eat larvae, nymphs and adults. The splashes you see on the surface are trout having a meal!

Nymphs and larvae breathe through gills. Mayfly gills are found along the sides of the abdomen. Stonefly gills re under the thorax. Caddis fly gills are hair-like filaments along the entire body. When the adult (imago) insect deposits its eggs in the water the eggs begin growing and dividing as they get bigger. The nymph and larval stages go through several moultings, periods between which are called “instars”, before they hatch, sometimes 20 or more. Mayflies go through one more moult as they turn from sub-imagoes to the egg laying imagoes.

PLECOPTERA (Stoneflies)

Swifter water, riffles, runs
One half to 2 inches long
Prominent tails and “feelers”
Twin sets of wing cases
Hairy gills under thorax
Two claws on each foot
Adults have two pairs of wings
Fly with body in vertical position
Wings folded flat over body when resting

TRICHOPTERA (Caddis flies)

One quarter to 2 inches long
Pale worms with “hooks” at the end of their bodies
Dark heads
Six legs attached to dark thorax
Hairy gills along abdomen
Larval stage stay sealed except for trickle of water
Swift water types swim to surface and emerge from pupal skin
Slow water species crawl to shallows and emerge like stoneflies
Pupae migrate to surface and emerge en-masse
Wings fold in an upside down “V”, like a pup tent, when at rest


Trout favorites
Three types of nymphs: burrowing, clinging and crawling/swimming
20 instars
Most nymphs have 3 tails
Restless before emergence, alerting trout and birds
At surface skin splits and DUN (imago) emerges, floats several feet
while wings stiffen
Moults again after flying to bushes
Reappears over water as SPINNER (imago) to mate a deposit eggs
Has four wings but rear set are small
Wings held erect while resting


Suggestions for further reading:
Matching the Hatch, Ernest Schweibert, Macmillan, New York, 1955
Nymphs, Ernest Schweibert, Winchester Press, New York, 1973
Aquatic Entomology, W. Patrick McCafferty, Science Books, Boston, 1981
Fishing the Nymph, Jim Quick, Ronald Press, New York, 1960

Prepared By: Steve La Falce


Arizona Council of Trout Unlimited


Adopted 6-5-2014

AZTU and the Arizona chapters of Trout Unlimited value and work to re-establish and preserve robust populations of native trout and their original streams and ranges in Arizona.  They are our first priority.

We also hold wild populations of non-native trout of great importance and constantly work to preserve them and the waters they occupy for the fisheries values they provide.

If it is not possible to establish a self-sustaining population of native or wild trout in a water system, AZTU and individual TU Chapters may elect to support alternate means of providing fish for sport-fishing purposes.

We have established clear guidelines and procedures to assure that any actions we take regarding all these fishes, their streams and ranges, are well thought out.

Ref: The Arizona Council of Trout Unlimited

Native And Wild Non-Native Salmonid Management Position – ADOPTED 2014-04-03

Western Native Trout Initiative (WNTI)

The Western Native Trout Initiative (WNTI) was formed in 2006 to incorporate the best conservation strategies of existing ventures to save trout that many regard as icons of the American West.

The 21 native trout and char addressed by WNTI have long been considered as biologically, recreationally and culturally important. While local conservation actions have occurred, overall range-wide recovery and coordinated management of western native trout and char generally has been addressed in a fragmented approach.  By working together, the partners in WNTIstrive to implement the most strategic actions needed to benefit these trout and char.  And by working together to establish secure populations, WNTI will also benefit anglers by enhancing recreational fishing opportunities for unique trout species across the West.

The Arizona Council of TU has been fortunate to be a recipient of several grants to advance the commitments of WNTI (

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7th Annual Native and Wild Trout Conference
April 21, 2016
9:00a.m. – 4:30p.m.

8:55a.m.       Pre-Conference Slide Program  

9:00a.m.       Welcome and Introductions  –

Mike Anderson, AZGFD

9:05a.m.       Welcome from the Arizona Game and Fish Department

9:15a.m.       AGFD Legislative Update –

Jorge Canaca: Legislative Liaison; AGFD –

9:30a.m.       AGFD Coldwater Fisheries Vision and Management Plan – 

Andy Clark – AGFD 

10:00a.m.     Trout Unlimited Southwest Native Trout Strategy –

Jack Williams & Brad Powell – Trout Unlimited

10:30a.m.     Glen Canyon Dam: Long Term Experimental Management Plan

Chris Budwig, PhD & John Jordan – Trout Unlimited

10:45a.m.     Break

11:00a.m.   Temperature Monitoring Network – 

Dan Isaak – US Forest Service (webinar)

11:30a.m.   Distinguished Service for Conservation Awards –

John Jordan & Gary Stinson – Trout Unlimited

11:45a.m.  Group Photo

 12:00p.m.  Lunch  

1:15p.m.     Elements of Good Stream Monitoring Programs –

Dan Dauwalter – Trout Unlimited

1:45p.m.     Western Native Trout Initiative (WNTI) Programs –

Therese Thompson – WNTI Coordinator of Strategic Partnerships

(a) 2:15p.m. US Forest Service-Wildfire Risk Assessment –

Tessa Nicolet – US Forest Service 

2:45p.m.     BREAK

3:00p.m.     Making Hatcheries Work for Native Trout –

Nate Wiese: USFWS – Mora National Fish Hatchery 

3:20p.m.      Trout-In-the-Classroom (TIC) Program –

Jennifer Johnson – USFWS: Angela Mitchell – Shea Middle School
Josh Ruddick – Santa Rita High School; DJ Zor – Trout Unlimited

5:00 p.m.    BBQ Dinner:  Sponsors & Directions to Biscuit Tank &                Educational Building

4:30p.m.     Adjourn / “See You Next Year”


The Sixth Annual Arizona Native and Wild Trout Conference was at the AZGFD Headquarters on Thursday, April 23, 2015.   The conference was co-sponsored by the Arizona Department of Game and Fish and the Arizona Council of Trout Unlimited.

The conference is attended by those interested to meet, network, and develop future plans to promote restoration and management of native and wild coldwater fish species in Arizona and New Mexico. Over 100 individuals attended the conference representing more than 35 agencies and organizations involved in water conservation and management, trout recovery and habitat enhancement.

Agenda and Presentations

(Presentations are in PDF Format, Click on to View)

NWTC 2015 Final Agenda and Schedule (PDF)


Arizona Game and Fish Department Headquarters
5000 W. Carefree Highway, Phoenix, AZ

Food and Lodging

Free lunch was hosted by AZ Sportsmen for Wildlife Conservation and AZ TU Council.

A free post-conference BBQ was hosted by the Arizona Council of Trout Unlimited.


The 2014 Arizona Native and Wild Trout Workshop was sponsored by Arizona Game & Fish Department and the Arizona Trout Unlimited State Council.Participants from over 30 Organizations gathered in Phoenix to network, share knowledge, and to develop and promote future plans for native and wild coldwater fish species in Arizona and New Mexico.April 24, 2014

April 25, 2014
Field Trip – Gila Trout Restoration Site Grapevine Creek
Sponsored by Arizona Game and Fish Department and Arizona Trout Unlimited State Council
Led by Mike Anderson, AZGFD


The 2012 Arizona Native Trout Workshop was sponsored by Arizona Game & Fish Department and the Arizona Trout Unlimited State Council.

**View welcome video from Chris Wood, CEO of Trout Unlimited!

Interested parties gathered in Phoenix to network, to share knowledge, and to develop and promote future plans for native coldwater fish species in Arizona.

This year’s meeting was highlighted by presentations on the the devastating effect of wildfires on Arizona’s native trout, and on the efforts to restore their natural habitat.

A wealth of information was developed through presentations, breakout sessions and general discussions. The following materials and presentations are now available for free download:

(media to follow)