Giant Salmonfly

Fishing season opened last weekend. Of course, Leonard HAD to do some catch and release fishing on Ash Creek (Lassen County CA) opening day. For me, the wildflowers were blooming in profusion!

It was a beautiful day and the air was thick with insects. One of the most “spectacular” insect this time of the year is the giant salmonfly (Pteronarcys californica), a type of stonefly. Over two inches long, this resident of Western North America is difficult to ignore, especially when it lands on you.

Giant salmonflies require streams and rivers with cool, rapidly flowing water that is well oxygenated.

The giant salmonfly has three life stages: egg, nymph and adult. Adults have two “tails”, two pair of wings kept flat against the body when at rest and orange abdomen, leg joints and thorax joints. The remainder of the body is brown. The adults spend most of their time on streamside foliage where mating occurs. Egg-laden females return to the water with their abdomen hanging down and briefly touch the water and release an egg cluster, which then sinks to the bottom.

The nymphs which hatch from the eggs are brown and take two to four years to mature, depending on temperature and food availability. Living under or clinging to the base of rocks and stones in the water, giant stonefly nymphs eat partially degraded stream debris. When mature the nymph crawls to the shore or onto a rock above the water where its exoskeleton splits to release an adult that is ready to mate. Depending on the water temperature, the heaviest emergence of giant salmonflies occurs at dawn or dusk.

Giant salmonfly nymphs or adults are available to trout throughout the year. The large size and distinctive coloration of a giant salmonfly make their “hatch” difficult to miss.

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