It felt far too early in the year for an egg hunt – and much too cold to be surveying butterflies. Yet, when it comes to searching for evidence of one of Britain’s most elusive lepidoptera, the timing couldn’t be better.
More than 20 of us gathered on a chilly morning in Belvidere Meadows nature reserve, on the outskirts of Exeter, to take part in a butterfly egg hunt organised by Devon Wildlife Trust. The progeny we were hoping to find were those of the brown hairstreak butterfly (Thecla betulae), a scarce chocolate- and orange-coloured species that is notoriously difficult to spot, as adults generally fly high up among the treetops.
“It’s easiest to survey them by finding their round white eggs, which are laid on young stems of blackthorn,” Simon Bates, of the trust’s Exeter group, told assembled volunteers. “They’re only the size of a pin head, but quite conspicuous against the dark bark once you get your eye in.”
The grassland reserve sloped down towards the River Exe, and around the wooded margins blackthorn grew in dense thickets, spiny twigs plucked clean of autumn’s sloe bounty. We spread out to search sheltered south-facing areas beneath stands of ash, and it wasn’t long before the first excited calls went up as individual eggs were detected and people gathered with magnifying glasses to take a closer look.
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Brown hairstreak butterflies are notoriously difficult to spot. Photograph: Rex/ShutterstockIt took a while to adjust my focus to such a micro scale, so I was delighted when a tiny pearl eventually caught my eye, nestled in the crook of a thin branch close to the ground. Viewed through a lens, its exquisite geometrical patterning gave it a frosted quality, a crystalline beauty that resembled a miniature growth of coral.
The brown hairstreak is one of nine UK butterfly species that overwinter in the egg stage, and is particularly vulnerable to seasonal hedge trimming. Once widespread, it is now restricted to scattered areas in southern Britain, and our survey was the first to confirm its presence in this reserve, with more than 50 eggs found during two hours of searching.
All being well, this precious next generation will be on the wing by late summer: once more dotting the woodland edge with fresh broods for keen-eyed enthusiasts to find.