TThe River Wharfe arboreal corridor is brightly lit by the sharp, tangy colours April brings: the fresh lemon and lime fuzz of hawthorn budsburst, the icy white of wood anemones, and the acidic yellow from willow catkins. The sunlight is diffused through a cloud sheet, creating a sense of gauzy elegance. Although much of the landscape is still pallid from winter, these first stabs in colour have a vitality that amazes me.
After a few weeks of volatile, cold weather, serenity, and sunshine suddenly returned, reviving the energy of spring. I look closer at the river and I see what I was looking for: a steady flow of small brown insects that fly upstream, just above the water’s surface, much like a soft horizontal snow.
In previous years, I have seen this phenomenon on April day like this. It is only visible in a window of about a fortnight. The air must be still and the air must be windless. Although I am not an entomologist, I have spoken to experts who believe it to be the mass hatching grannoms.Brachycentrus subnubilis)a type caddisfly.
These moth-like, small insects have a fascinating life cycle within the river. Lapteres wrap themselves in a protective tube of silk, which they then add to with bits of vegetation and other debris. Once the pupae are ready, a rise of water temperature causes them to float to surface in large numbers and emerge as adults. Some species use their discarded shells for a raft and float on the water surface until dry enough to fly.
Although they might seem small, the sheer scale of their emergence is truly remarkable. For days, hundreds of bugs stream past each other every minute, and water slack sections simmer with ripples while they fly, eventually rising into spring.