The heavyweights of the aquatic insect world, this month’s critter of the month are stoneflies.
These are an order of insects known as Plecoptera, which roughly translates to “braided wings” in reference to the heavily veined wings found on the adults. Despite these wings, the adults are known as clumsy fliers and if you have ever seen them on your favourite river, you will know why – the adults seem to fly around, buzzing and looking like old miniature helicopters trying to carry a heavy load. They are highly successful insects though, found all over the world – except Antarctica - and there are around 3500 different species that have, so far, been discovered.
Like many aquatic insects, stoneflies have aquatic and terrestrial phases of their lifecycle, with nymphs typically found on the bottom of well-oxygenated rivers and freshwater lakes. Nymphs may spend up to 4 years underwater, continually shedding their skin and slowly developing while they do so. At this stage they may eat plants and algae from the stream bed or hunt other aquatic insects for food. When the time is right, the nymph will crawl out of the river and attach itself to a rock, branch, reed or any other solid object and undergo one final moult before ‘hatching’ into an adult. During the few weeks of adulthood, stoneflies will generally stick around their home streams and mate so the next generation of eggs can be deposited in the stream by the females to continue the lifecycle.
Having stoneflies on your home stream is good for a number of reasons. One is that they are great indicators of water quality – stoneflies really don’t like pollution and only survive in the cleanest of streams. This makes them a good example of an indicator species. Another reason they are good to have on your home water is that fish love ‘em! Imagine being a trout, sipping on tiny midges all day, and suddenly a big stonefly comes drifting down the river! That big, meaty meal provides a lot of energy to fish and many species will go out of their way to feed on them. This is why, more than any other, a hatch of stoneflies is coveted by fly anglers, who tie on huge dry fly imitations up to a couple inches long to try to tempt the big trout that can’t resist rising to this epic hatch. See the video below for more tips on finding stoneflies on your river.
Video Credit: Orvis
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