Unraveling the Differences: Salmonfly vs Stonefly for Fishing

When exploring the world of insects, you may come across two fascinating species: the salmonfly and the stonefly. Both of these intriguing insects play vital roles in their respective ecosystems, providing valuable insight into the health of rivers and streams. While they may appear somewhat similar, there are key differences between the two that are worth exploring.

Salmonflies are large, robust insects that are commonly known for the essential role they play in the life cycle of fish. As they are a primary food source for many species, including the highly prized trout, understanding the salmonfly can greatly enrich your appreciation for the interconnectedness of nature.

On the other hand, stoneflies are a diverse group of aquatic insects that can be found in a variety of colors and sizes. With their threadlike and long antennae and unique wing structure, these insects are easily distinguishable from salmonflies. Notably, stoneflies play a vital role as bioindicators, meaning their presence or absence in a water body helps provide insight into the water quality and overall health of the ecosystem.

Salmonfly vs Stonefly: A Brief Overview

When you come across a salmonfly or a stonefly, you might wonder what sets them apart. They both belong to the order Plecoptera, but they have distinct features and belong to different families.

Salmonflies are aquatic insects from the family Pteronarcyidae, with Pteronarcys californica being the most well-known species, commonly known as the American salmonfly. Salmonflies are usually larger in size and can be found near fast-moving streams.

Stoneflies, on the other hand, can belong to various families within the Plecoptera order. One example is Pteronarcys dorsata, known as the giant stonefly. Stoneflies are commonly found near both slow-moving and fast-moving water sources.

Below is a comparison table to help you understand some differences and similarities between these two fascinating insects:

Feature Salmonfly Stonefly
Family Pteronarcyidae Various families
Size Larger Variable
Habitat Fast-moving streams Various water sources
Metamorphosis stages Larva-Nymph-Adult Larva-Nymph-Adult
Diet Aquatic algae, detritus, other insects Aquatic algae, detritus, other insects

Some characteristics shared by both salmonflies and stoneflies include:

  • Being part of the Arthropoda phylum and Insecta class
  • Undergoing incomplete metamorphosis (egg, nymph, and adult stages)
  • Having two antennae and variable wing sizes
  • Contributing to the ecosystem as a food source for fish and other predators

Now that you have a brief overview of salmonflies and stoneflies, keep an eye out for these aquatic insects when exploring rivers and streams. Pay attention to their size, habitat, and other unique features to distinguish between these captivating creatures.

Comparing Size and Physical Attributes

Size Comparison

Salmonflies and stoneflies are both aquatic insects belonging to the order Plecoptera. They have some differences in their physical attributes. When it comes to size, you’ll notice that the salmonfly is generally larger than the common stonefly. For example, the salmonfly Pteronarcys californica can grow up to 5 cm in length, while typical stoneflies measure around 1 to 3.5 cm.

Color Variations

The colors of these insects also differ. Here’s a simple list of the common color variations you may find in both species:

  • Salmonfly: Red, black, or brown
  • Stonefly: Brown, gold, gray, green

Color variations are often found in the exoskeletons of these insects, which come in a range of shades and patterns. Besides size and color, other physical attributes also set them apart. Salmonflies and stoneflies have different features in terms of wings, eyes, legs, and antennae.

Salmonflies have wings that are more wide-set when compared to stoneflies. Additionally, the eyes of a salmonfly are relatively smaller when viewed alongside those of a typical stonefly. Both species have six legs, but their structure and proportion can differ slightly. The antennae of salmonflies are usually shorter and thicker than those found in stoneflies.

In summary, when comparing salmonflies and stoneflies, be mindful of their size differences, color variations, and other distinguishing physical attributes. By doing so, you’ll be better equipped to identify them and appreciate their unique features in aquatic ecosystems.

Life Cycle and Hatch

Understanding the Life Cycle

Salmonflies and stoneflies are both types of aquatic insects. Their life cycles consist of four stages: egg, nymph, adult, and larva. During the nymph stage, these insects go through a process called molting. This is when they shed their exoskeleton in order to grow. While molted, the nymphs are called larvae.

Both salmonflies and stoneflies reach adulthood through a process called emergence. This is when the nymphs swim to the water’s surface, break out of their exoskeletons, and unfold their wings. In a short period of time, the adult insects dry their wings and take flight.

Hatch Seasons

The hatch seasons of salmonflies and stoneflies are quite distinct. Salmonfly hatch usually occurs in late spring, depending on the timings of river flow and temperature. On the other hand, stoneflies hatch at different times throughout the year with peak hatching in late winter and early spring, depending on the species.

Here is a comparison table highlighting the main differences between salmonfly and stonefly life cycles:

Feature Salmonfly (Giant) Stonefly
Life Cycle Stages Egg, Nymph, Adult, Larva Egg, Nymph, Adult, Larva
Molting Yes (as nymphs) Yes (as nymphs)
Emergence Late spring Late winter/early spring
Hatch Duration Short Varies by species

Overall, understanding the life cycles and hatch seasons of these aquatic insects can help fly fishers better prepare and select the right flies for catching fish that feed on them.

Habitats and Geographic Regions

Salmonflies and stoneflies both belong to the order Plecoptera and share some similarities in their habitat preferences. However, there are differences in their geographic distribution and specific habitat requirements.

Salmonflies are found in freshwater rivers with strong currents. These rivers usually have a rocky bottom, with boulders serving as the ideal habitat for them. You’ll mostly find them in regions of Canada and the United States, such as Montana.

On the other hand, stoneflies inhabit a wider range of freshwater habitats, including rivers, streams, and lakes. They’re known to thrive in environments with plenty of algae, serving as a food source for detritivores like them.

  • Salmonflies:
    • Freshwater rivers with strong currents
    • Rocky bottoms with boulders
    • Canada and Montana in the United States
    • Prefer colder water temperatures
  • Stoneflies:
    • Rivers, streams, and lakes
    • Varied bottom substrates
    • Widespread across North America
    • Tolerate a broader range of temperatures

In conclusion, both salmonflies and stoneflies are essential components of freshwater ecosystems and serve as excellent bioindicators for water quality. While they share some similarities, understanding their unique habitat requirements and geographic regions can help you better appreciate and conserve these fascinating insects.

Fishing with Salmonflies and Stoneflies

Fly Fishing Techniques

When fly fishing for trout, you can use salmonflies and stoneflies as effective bait. These insects are a natural food source for fish, making them highly attractive to various species. Salmon flies, also known as Pteronarcyidae, and stoneflies (Plecoptera) are widely used by fly anglers due to their lifelike appearance and movement in the water.

When fishing with salmonflies and stoneflies, you can adopt two main techniques: nymph fishing and dry fly fishing. For nymph fishing, you’ll mimic the behavior of the insect’s underwater stage, using weighted nymphs to sink your fly to where the fish are feeding. When the nymphs are ready to emerge, they swim towards the surface, becoming prey for trout. Dry fly fishing involves using unweighted flies that float on the water’s surface. As adult salmonflies and stoneflies lay eggs on the water, fish feed on these insects, making the dry fly technique effective.

Examples of stoneflies for fly fishing:

  • Golden stone (Hesperoperla pacifica)
  • Skwala (Skwala americana)
  • Black stone (Leuctra ferruginea)
  • Yellow Sally (Isoperla bilineata)

Suitable Bait

Fly anglers often create their bait using materials like feathers and fur, replicating the appearance of stoneflies and salmon flies. Here are some popular fly patterns for each insect type:

Stonefly patterns:

  • Large golden stones
  • Black stones
  • Yellow sallies

Salmon fly patterns:

  • CDC salmon fly
  • Mayflies

An essential aspect of choosing suitable bait is matching the correct size, color, and profile of the natural insects present in the water. Observing the natural insects in the area before making your bait selection will help increase your chances of success. Another tip is to ensure that your hooks are barbless, which makes it easier to release the fish without harming them.

Remember that using the right bait, combined with proper fly fishing techniques, will increase your chances of success when fishing for trout using salmon flies and stoneflies. The goal is to mimic the natural behavior and appearance of these insects, which will, in turn, attract more fish to your hook. Happy fishing!


In summary, both salmonflies and stoneflies share similarities in their roles within aquatic ecosystems. They serve as essential indicators for water quality, and their presence in a stream signifies a healthy environment1. Let’s briefly compare their main characteristics:

Feature Salmonfly Stonefly
Habitat Streams and rivers Streams, rivers, and ponds
Size Larger (up to 3 inches) Smaller (under 2 inches)
Lifecycle stages Egg, nymph, and adult Egg, nymph, and adult
Food Algae, plants, detritus Algae, plants, detritus

A few key differences between these two insects include their size, with salmonflies typically being larger than stoneflies2. Despite these differences, both types of insects play essential roles in monitoring the health of our streams and water systems.

Next time you’re near a body of water, keep an eye out for these fascinating creatures and appreciate their contribution to maintaining the balance of our ecosystems.


  1. Stoneflies and mayflies, canaries of our streams
  2. Stoneflies | Missouri Department of Conservation

Reader Emails

Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.

Letter 1 – American Salmonfly


Subject: Identify
Location: NE Pennsylvania
April 28, 2017 7:04 pm
Can you please tell me what insect this is?
Signature: Ken Brendel

American Salmonfly

Dear Ken,
This is a Giant Stonefly in the genus
Pteronarcys, and based on your location and this image on BugGuide, we believe it is the American Salmonfly, Pteronarcys dorsata.

Letter 2 – Midwestern Salmonfly


Subject:  What is this bug?
Geographic location of the bug:  South Central Wisconsin
Date: 06/12/2019
Time: 02:27 PM EDT
Your letter to the bugman:  Hi,
We have found TWO of these bugs in our home in the last 12 hours. We live in a small city, but our house is at the end of a street adjacent to farm fields. Given the amount of rain we have had this spring, there is standing water in some areas of the fields not far from our house. I have never seen any of these bugs before that I know of, but especially not in our house. Last night’s sighting including the bug crawling up from the inside of a new reclining chair!
How you want your letter signed:  K

Midwestern Salmonfly

Dear K,
This is a Giant Stonefly or Salmonfly in the genus
Pteronarcys.  Based on your location, we are surmising this is a Midwestern Salmonfly, Pteronarcys pictetii, which is pictured on BugGuide.


  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. whatsthatbug.com is his passion project and it has helped millions of readers identify the bug that has been bugging them for over two decades. You can reach out to him through our Contact Page.

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  • Piyushi Dhir

    Piyushi is a nature lover, blogger and traveler at heart. She lives in beautiful Canada with her family. Piyushi is an animal lover and loves to write about all creatures.

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