Country diary: An eruption from the river, like a fountain of sparks

Broughton, North Yorkshire: Whatever flies they were, this was the most beautiful and most holy expression of spring I’ve witnessed this year

The stream known as Broughton Beck was calm, so looking downstream with the late‑afternoon sun, I saw it as an unperturbed linear plane widening to a deep black pool beyond the bridge. Looking upstream, I was confronted by a fierce double glare. There was the light dazzle on the shallows, splintered into linear flakes as it flowed towards me. It was mesmerising.

Yet it was nothing compared with the brilliance of the insects above the stream. I’ve struggled subsequently to name them, but they were not mayflies or caddisflies, nor any of the invertebrates classically associated with freshwater in high spring. They were some species of fly, possibly a member of the order Muscidae (house flies) or Anthomyiidae (root-maggot flies), and present in astonishing numbers. Over two days I must have seen many hundreds of thousands on almost every waterbody at Broughton, from any hilltop rill to the secondary streams around this ancient estate.

The main appearance was on the beck. Formless glittering shoals upwelled from the stream's meniscus and spilled outwards like a fountain of sparks. All over the flat surface of the river, from one side to the other, more flies skated randomly back and forth. The most intense showing was a linear formation running relentlessly up and down the line of the beck.

I guess they were in some ritualised mating display, which is known in other fly species as a "ghost". However, there was nothing unliving about this vision. It was life expressed in its most elemental and volatile form, like a flow of electrons, or photons at the heart of the Sun. The movement was so unceasingly quick that it felt as if I was at the edge of what my brain and visual system could embrace. This was odd, because while their collective action was so disturbingly brilliant, if I picked out a single individual by itself, and then globed it in the whole of my attention, it was just your average slow-floating fly. Let it merge, however, back into the silvered smoke of the whole thing and it reunited with the most beautiful and most holy expression of spring that I’ve witnessed in 2023.

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