Many hundreds of species of insects, common and rare, live in the Kennet. Many, like dragonflies, caddisflies and mayflies have a larval stage that lives underwater, and an adult stage that flies above it.
Above: Cased Caddis Larvae
Others, like water beetles and water bugs, live in, or on, the water all year round. The Kennet is noted for its large hatches of mayflies, whose long-tailed, short-lived adults are a favourite food of trout. One of the more conspicuous is the large, yellow-bodied Ephemera danica, the angler's 'drake'. Caddisflies are also very numerous, especially in late summer when they come to lighted windows and street lamps. Their larvae make expertly-built little cases of stones or plant debris, usually attached to a stone. To find such hidden insects, you need to be a dedicated stone-turner. But remember to replace them as you found them.
The river is too fast for most dragonflies, but one you see often flapping lazily along well-vegetated margins in midsummer is the Splendid Agrion. The males have bright blue spots on each wing, making them almost butterfly-like. Another brightly-coloured insect that appears at the same time is the Scarlet Tiger Moth, which flies by day, and can also be found at rest on flower-heads. Its caterpillars feed on comfrey leaves, and can easily be found by searching in the spring: they are black with a yellow stripe, hairy and about an inch long. The Kennet valley is home to several hundred kinds of moth, from big Privet and Poplar Hawks to tiny ones that fly up when you walk through tall grass at the river's edge. There are even a few, known as China-marks, whose caterpillars live under water. On the other hand, butterflies are not particularly numerous. Large colonies of Small Tortoiseshell and Peacock caterpillars have been found in nettle beds near the river, and Orange-tip caterpillars on Lady's Smock and Hedge Garlic pods.