Diptera in the Brownfields

23 April 2022

Fifty years ago, when Britain was still re-building after the war, brownfield sites were common. Condemned houses no one had bothered to demolish, derelict factories bankrupted out of business, even disused railways, littered urban areas. It didn’t take much for nature to move in, and while we were warned not to go too close, most of us children, on a sunny afternoon, couldn’t help but explore. Personally, I avoided the houses and factories, but the old village station drew me back again and again.

All that was left of it by then were three roofless walls and some tracks hidden in the long grass. Opened in 1849, it transported troops to the nearby training camps during the Crimean War. Quickly superseded by more direct lines, it hung on throughout the First World War, but closed for passengers in 1937. It carried freight up to 1960, becoming more unkempt each year as the grasses took over and the sidings sprang forests of bramble and sloe. Over a decade later when I was looking for moths on the damp walls and watching the butterflies land on the teasels, it was a dense mix of ruderal scrub and established woodland.

Brownfield sites are valuable places for many species squeezed out of their habitat by our relentless urbanisation. While the mice and moles of the 1840s felt the sharp end of progress, their descendants were quick enough to reclaim the station in the 1960s. In all my wanderings about looking for beetles and avoiding wasps, I never dreamt to look for picture-winged flies; I never knew they existed. To me, crouching in the fleabane, they would have been extraneous matter caught in the clouds of dust above the metal tracks: pollen, seeds, invertebrates. Irritable in the heat, nauseous with the stink of bryony and burnt rail, I would have confused them with midges and swatted them away.

Either herbivores or detrivores, Ulidiidae are scavengers. Most species found in the UK are between 4mm and 10mm long and many go unnoticed at the damp edges of ponds or hiding in the hedgerows. But if you do see them, you don’t forget them; their wings really do show pictures. Spots, stripes, symmetrical patterns, often black or brown on white. Seen close up they are beautiful, delicate, distinctive: Herina frondescentiae with its black and white bands; Melieria crassipennis with its brown dots and Otites guttata with its mottled wings. All are imbued with a curious, silent grace.[i] The NBN Atlas holds 3653 records of Ulidiid flies, and a swift glance at the map shows a high density in the southwest with sightings spread sporadically across the country.[ii] The surveys tell us that picture-winged flies proliferate brownfield sites, being among the most successful colonisers of these damaged spaces.[iii]

The old railway is long gone, replaced by new roads and houses. Where I live now, I haven’t seen a brownfield site for years – as fast as each old building is sold, new apartments spring up in its place. We are living though a building revolution and the continued expansion of our urban environment cramps the natural world into smaller and smaller sites. The picture-winged flies thrive in damp, rotting places, feeding off age and decay – decomposing wood, dank fields, dung piles. They find their niches, but we keep taking the niches away. Efficient recyclers, converting detritus into nutrients, making resources out of rubbish, we need them for practical reasons way beyond aestheticism; mini-resurrectionists, they work their magic turning death back into life. Impeccably dressed and invariably overlooked, they are invaluable in the struggle to clean up the mess we leave behind us wherever we go.

[i] https://www.naturespot.org.uk/family/ulidiidae

[ii] https://species.nbnatlas.org/species/NBNSYS0100005929

[iii] https://www.bsg-ecology.com/research-into-creation-of-open-mosaic-habitat-for-invertebrates-at-a-brownfield-site-in-peterborough/