Searching for the presence of an elusive butterfly

Rob Eadie, Volunteer Reserve Manager, Levin Down

This month I have been searching the spiny Blackthorn branches on Levin for the tiny eggs of the Brown Hairstreak Butterfly. Despite being the size of a pinhead, the eggs are often surprisingly bright, and quite easy to spot against the dull background of winter stems.

Laid in the autumn, the eggs will remain dormant through the winter and hatch in the spring, when the fresh leaf buds will provide food for the young caterpillars.

Counting the eggs in winter can be the easiest way to establish the presence of this butterfly, as the adults can be elusive. They fly only in late summer, and tend to stay high up in taller trees, where they congregate to feed and mate.

So far I have counted four eggs, all within a small area of Blackthorn scrub. This is an exciting discovery, as there have been few recent records of Brown Hairstreak on Levin. It is good to know that they are still resident on the reserve.

The Brown Hairstreak is a listed UK BAP priority species, and in need of protection. I will continue to search for eggs in other parts of the reserve, and there are now plans to coppice some of the mature Blackthorn. This will ensure that there is a good supply of fresh young shoots for future egg laying females.

It would be nice to ensure that this beautiful and charismatic butterfly continues to grace the slopes of Levin.