Brown Hairstreak
Thecla betulaeThe Brown Hairstreak spends most of its life high in tree canopies. It is often one of the last butterflies to emerge in summer, but enjoys waking up early to make the most of the morning sun. As caterpillars, they glow under UV light, a handy quirk for the scientists who track them. Found along hedgerows and woodland margins in central and southern Britain, this butterfly is increasingly rare due to habitat loss.
A glowing light in the hedgerow
The Brown Hairstreak starts its life as quite a funky little caterpillar. They glow in the dark, and scientists use UV torches to help monitor their population levels.
This butterfly is usually one of the last to emerge from their chrysalis each summer. Keen to make up for lost time, they aren’t afraid of an early morning and are most active first thing.
With its habit of hiding high in the trees, spotting this butterfly can be tricky, but they do sometimes congregate in groups as they flit about the canopy in an erratic zig-zagging flight looking for honeydew.
Brown Hairstreaks may appear delicate with their tiny tails, scalloped wing edges, and pale orange underwings, perfect for blending with autumn foliage, but this butterfly will brave Bramble to feast on its flowers.
To find Brown Hairstreaks, you’ll need to be in central and southern Britain. Look for them along hedgerows and woodland margins.
Sadly, though, this brown beauty has recently undergone a massive decline due to annual trimming of hedgerows. This removes the leaves their eggs are laid on and disturbs their breeding cycles. With many hedgerows also being removed completely, they’ve been running out of safe places to call home.
Vibes
Each butterfly is scored out of 100 across a set of traits, from how bold and visible it is to how far it travels or how particular it is about where it lives. These scores compare each species with the other butterflies in Britain, helping you see their differences at a glance. Here’s what makes the Brown Hairstreak special.
Bright colours, bold patterns, and a love of the spotlight. Some butterflies just can’t help showing off.
Fast, or throwing some seriously impressive moves, these butterflies are in a flutter.
Always on guard, ready to hide or defend - these butterflies have self-preservation down to an art.
It’s ok to be a little… well, weird. These butterflies have been certified with the freak factor.
Like Goldilocks, everything has to be just right for these perfectionists.
Hard to spot and even harder to forget, these butterflies are a true one of a kind.
Bold, curious, and ready to explore, these brave butterflies live for the thrill and aren’t afraid to travel.
Weather-resistant, battle-hardened, and built to survive, these butterflies know how to take it on the wing.
Brown Hairstreaks are delicate in appearance but will brave Bramble to get to their flowers.
Test your knowledge
How do scientists help monitor Brown Hairstreak caterpillars?Brown Hairstreak caterpillars can be detected using UV torches because they fluoresce, helping scientists monitor populations more effectively.
Does the Brown Hairstreak get your vote?