Alder fly

06.07.2002

Ó Robert Burton

I photographed these insects on the bank of a gravel pit. At first I thought they were caddis flies or perhaps lacewings, on account of the long antennae and the wings folded over the back like a pitched roof. But they are alder flies. These relatives of the lacewings are reluctant fliers, which explains why it was so easy to take their pictures. The left-hand photo shows a pair mating and even less willing to fly.

Alder flies are very unremarkable insects. The adults do not feed and are short-lived. They have to breed within a few days, before they die of starvation or are eaten. They lay their eggs in batches by the waterside and the emergent larvae crawl or fall into the water. They spend about a year living an active life preying on the larvae of mayflies and caddis flies and, in due course, crawl ashore to pupate. They burrow into the soil and, about three weeks later, emerge as adult insects, and the cycle starts again.

It is rather an un-Noteworthy way of life but one little 'nugget' of information caught my attention. The larvae may crawl several yards from the water's edge in search of a place to pupate. This seems unnecessarily far, but one alder fly larva was seen to travel as much as 6 yards, over a concrete wall and through some shrubs to an open flower bed. It sounds like one of those people who undertake some purposeless feat of endurance just to get into the record books.