Country diary: the caddisfly larvae are emerging, creatively camouflaged

The vegetation at the bottom of my pond stirred, and three small clumps sprouted legs and began creeping up the side. About an inch long, one resembled a sprig of gorse, bristling with short lengths of foliage, while the second was a similarly compact cluster of stems topped with a water snail shell, as if added for decoration.

The third, motoring slowly over the algae toward me, with a piece of birch catkin for a front bumper, was a more disorganised jumble of bark and plant snippets, some pink as sticks of rhubarb. Occasionally, the inhabitants of these cumbersome constructions revealed themselves, as they reached forward, pale-bodied with long front legs and a head banded with chestnut brown – the secretive larvae of caddisflies.

Using sticky silk, these soft-bodied freshwater dwellers bind together material in ponds and streams to build their camouflaged mobile homes, in which they eventually pupate before hatching out as flying adults. And the differing designs can help to identify the species from the many dozen that inhabit our waterways.

Some assemble a slim tube of weed clippings laid lengthways, others a neat pebbledash covering of gravel. And they have even been encouraged in aquariums to fashion their temporary protective cases with precious stones to create unique and intricate pieces of jewellery. The Jenga-style arrangements visible in my pond appeared to broadly match descriptions for the common cinnamon sedge, or Limnephilus, group of caddisflies.

Entomologists are not the only experts in the lifecycle and appearance of these intriguing insects. Trout anglers tie artificial flies to imitate the immature stages as well as the moth-like adults, with their forward-pointing antennae and wings held in a tent shape over their backs at rest.

Feeding trout will readily snaffle caddisfly larvae, crunching them up like hard sweets with soft centres, and take adults from the surface when they hatch in large numbers during the warmer months. Watching my surreal trio lumbering along the pond side, I had to admire their resourcefulness – even if they did all look like they had crawled through a hedge backwards.

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