Stream Macroinvertebrates

December 2009

The Bear Creek Watershed Virtual Tours were created with funds provided by the

Bear Creek Watershed Education Partners through a grant from the

Oregon Watershed Enhancement Board with additional funding from Oregon Trout’s Healthy Waters Institute.

THANKS TO: •Kathleen Donham•Brandon Goldman

•Jefferson Nature Center•Maya Cross-Killingsworth

Vertebrate or invertebrate?

What is a vertebrate?An animal with a spine (vertebrae).

What is an invertebrate?An animal without a spine.

Macro means: you can see the animal with your naked eye.

Vertebrate or invertebrate?

On Earth: all life forms vs. invertebrates

On Earth: invertebrates vs. invertebrates

So, what is a macroinvertebrate?An animal without a backbone

that can be seen with the naked eye (without a microscope).

The group of invertebrates with the most species is the Arthropods

Arthro + pod

Arthro = jointed appendages

Pod = legs

Among the arthropods, the group with the most species is the insects.

What makes an arthropod an insect?

• Three body parts• Six legs• Wings• Antennae • Specialized mouthparts

Life cycle of an insect

Complete metamorphosis Incomplete metamorphosis

Complete metamorphosis means that the insect has a pupa or cocoon stage before becoming an adult.

Stream macroinvertebrates live in freshwater streams.The macroinvertebrates in the stream are usually insects in the larva stage of life. Some of them will

spend many months in the stream as a nymph or larva and only a short time as adults out of water. The larvae emerge from the stream at different times of year and

will then reproduce.

Stream macroinvertebrates are important to study because they can tell humans about the health of the stream.

Some stream macroinvertebrates are sensitive to pollution and other changes to their environment.

The presence or absence of sensitive macroinvertebrate species tells people about the health of the creek. How?

MayfliesThere are many species of mayflies found

in the streams of the Bear Creek watershed. Mayfly nymphs usually have three tails. To remember, hold your 3 fingers like the letter

“M” for mayfly.

Nymph

Mayfly nymphs are strong swimmers and feed on algae. Adults do not have working mouth parts and do not eat.

As adults, they may only live a few days. Mayfly diversity declines as streams are degraded.

Adult

CaddisfliesCaddis fly nymphs are known for the cases that many

species build using silk (like butterflies) and bits of sand, pine needles, or vegetation fragments.

Caddisfly larvae feed in a variety of ways; some capture food in nets, others scrape algae

or shred leaf litter.

Nymph

Many free-living caddisfly larvae do not build cases and are predators. They do not have a case because they need to move quickly to capture other animals for food. Some

caddisflies are very sensitive to human disturbance; others are more tolerant.

Adult

Stoneflies

Stoneflies nymphs have two tails. Adult males and females emerge from the water to mate in midsummer

and locate each other by drumming with their abdomens.

Nymph

Stoneflies are also called salmonflies and are predators that hide and stalk their prey between stones and

cobble. Stoneflies look similar to mayflies but are usually larger and stockier.

Adult

Note to user:

• Objective of presentation: brief introduction to stream macroinvertebrates.

• Most appropriate for: Ages 8 and up• How to integrate this presentation into other activities:

– Draw examples of insect life cycles.– Learn about local insects and the habitats they live in. Draw pictures

of these insects with their physical characteristics and in their habitats.

– Go to a stream and examine stream macroinvertebrates.– Find and identify insects in local vegetated areas.