Insect Habitat | CSKT | Division of Fish, Wildlife, Recreation, & Conservation

Habitat: Aquatic Insect Habitat

Aquatic insects—mayflies, stoneflies, caddisflies, and an assortment of aquatic beetles, flies, and bugs—are an integral part of any stream, each with unique habitat preferences. Select any habitat type (riffle, pool, run, glide) in a stream, and there will be a distinct group of insects adapted for that environment. In addition to providing endless diversity to a stream’s biological community, insects are a vital link between a stream’s energy sources and higher level consumers (i.e., fish). Energy inputs—whether from the riparian zone (leaves, sticks, pine needles) or within the stream (algae, aquatic plants, and periphyton)—drive stream systems. Aquatic insects aid in the transport of these energy sources up the food chain. This processing of energy is not only one of the primary ingredients to producing healthy native trout, it also ensures a healthy stream system. Aquatic insects also tell us how healthy the river is because aquatic insects are often very specific in their habitat requirements. Knowing where they live and why is key to understanding the river. Click on the letters below to explore aquatic insect habitat.

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Habitat: Aquatic Insect Habitat

Aquatic insects are a vital link between a stream’s energy sources and higher level consumers (i.e., fish). They also tell us how healthy the river is because aquatic insects are often very specific in their habitat requirements. Click on the letters below to explore aquatic insect habitat.

Click on the tabs below the image to learn more.

Click on a letter in the image to learn what insect lives there

A

A. Mayfly Habitat: Swimmers

Habitat for swimmers varies. Some streamlined nymphs shoot through the water, faster than fish of the same size, and they swim upstream against strong currents without a problem. But others inhabit slow water and use their speed to dart between leaves and other debris.

B

B. Mayfly Habitat: Burrowers

Often nymphs of burrowing mayflies are nocturnal. Their pale bodies are sensitive to the sunlight so they emerge only at night. They build U-shaped burrows into the stream bottom, where they feed on microorganisms in the sediments. They come out of these burrows to molt up to 30 times throughout their development.

C

C. Mayfly Habitat: Clingers and Crawlers

Clinging mayfly nymphs have flat bodies so they can cling tightly to rocks in fast currents. They hug the stones in riffles and rapids of cold or cool streams. They like cold water because the cooler the water, the more oxygen it holds. Clinging mayfly nymphs have to have high levels of oxygen in the water. And they cannot tolerate even low levels of pollution.

Crawlers are robust and blocky compared to other mayflies. They have strong, heavy legs and spend most of their time crawling because they are not good swimmers. They too, need cool clean water, although they are not restricted to riffles and rapids. Some crawler species live on detritus and aquatic vegetation.

D

D. Blackfly Habitat

Blackfly larvae are found in flowing water on stones, vegetation, and logs, usually in the swiftest part of the stream. Sometimes they occur in dense masses that can look almost like a coating of moss. They can be very abundant under sewage treatment plants, hence their tolerant pollution rating.

E

D. Stonefly Habitat

Stonefly larvae are commonly found crawling or hiding on stones in riffles of clean streams—their habitat is generally fast-flowing aquatic environments with rocky bottoms.

Stoneflies are known as clean-water insects because they need clean, oxygen-rich water. As such they are great biological indicators of water quality. They actually require a higher overall water quality than most trout.

F

D. Caddisfly Habitat

Caddisfly larvae live in a variety of micro habitats from riffles and rapids to pools and quiet waters. They can be found on all substrate types. Some live on aquatic vegetation. The soft bodies of some species are covered in protective cases. Some Caddisfly live in fixed homes, and some have mobile cases. Some species do not live in cases, using their hooks instead to cling to the stream bed. Caddis-Adult-2