As I strolled along the frosted path beside the Lymbourne stream, the stillness of the afternoon was fractured by a piercing screech. A child playing on the bank flailed her arms as she was engulfed in a shimmering cloud of tiny insects. Winter gnats (Trichocera sp.) – hundreds of them – ethereal against the starkness of the leafless trees.
They were likely T. annulata, the commonest of the 10 species found in Britain, though their appearances are so alike that they can be distinguished only by microscopic examination. Superficially similar to their cousins, the true craneflies (Tipulidae sp.), winter craneflies, as these gnats are also known, have filament-thin legs, banded abdomens and clear, unmarked wings but are significantly smaller, their bodies measuring between 6mm and 10mm. They also have ocelli on the tops of their heads. These simple “eyes” help them to keep their gaze level, stabilise their flight, detect light and orient themselves relative to the sun, which is particularly beneficial during the depths of winter.
As their name suggests, winter gnats appear in improbable abundance at this time of year. While most invertebrates hibernate or enter a state of diapause, these dainty flies thrive in cool, damp conditions. Lower temperatures concentrate populations, encouraging males to engage in lekking behaviour. Gathering in swarms referred to as “ghosts”, they perform courtship dances to attract prospecting females. Hovering, rising and dipping, each displaying gnat dances to its own rhythm while deftly avoiding collisions with rivals.
Adults are short-lived, dying within 10 days, but once mated, the females will oviposit in rotting vegetation or leaf litter, the emerging larvae entering dormancy during their final stage of development if conditions become too harsh.
Unlike biting gnats, the scourge of summer, winter gnats have no interest in feasting on human blood. However, as the weak winter sunshine barely produces heat, they are magnetically attracted to a warm body. Hurrying over, the girl’s parents grabbed her swatting hands, encouraging her to run. As the family surged forward, the swarm drifted towards me like smoke. Peppering my vision, the creatures encircled my head, forming a golden halo as their fragile wings caught the last light of the setting sun.
• Under the Changing Skies: The Best of the Guardian’s Country Diary, 2018-2024 is published by Guardian Faber; order at guardianbookshop.com and get a 15% discount
