This marker on the Cambridge Butterfly Trail is at St Albans Road recreation ground – see the map above.

The White-letter hairstreak is a small, elusive butterfly notable for the distinctive ‘W’ marking on the underside of its hindwings. It spends much of its time flitting invisibly in elm tree canopies, making sightings rare and special.

Adults frequently descend to feed on honeydew and occasionally nectar from flowers like bramble and privet. Its caterpillars feed exclusively on elm species such as wych, English and small-leaved elm, laying eggs near new season’s growth.

The species dramatically declined after Dutch elm disease decimated its food plants in the late 1960s, causing a national fall of roughly 78% in abundance. However, planting disease resistant elm cultivars like ‘Nanguen’ has begun to help populations recover in places.

Typically active from June to August, this butterfly has a single brood and is now a priority species for conservation efforts across England and Wales.

For more information, please visit Butterfly Conservation’s page on this species – White-letter hairstreak.