Saturday, 20 July 2013

Butterflies emerge as it warms up

The warm spell, whose arrival was perhaps uncharacteristically timed to the nation’s favourite sporting event, has delivered an upturn in the number of butterfly sightings locally. Most evident of these have been the small tortoiseshells, with numbers reaching double figures in a few chosen gardens around the Brecks. Further afield, in ungrazed grasslands and the scruffy margins of forest rides, the first of the summer skippers (small, essex and large) are being seen. There have even been reports of clouded yellow butterfly and hummingbird hawk-moth, both a sure sign of some decent summer weather.

This fine spell of weather suggests that it is also the time to be out looking for some of our more overlooked butterflies, including both white admiral and purple hairstreak. Both are woodland butterflies and both spend much of their time up in the tree canopy, only coming down to a lower level to nectar and take other nutrients. The graceful white admiral is on the wing from June to August, depositing eggs on the leaves of honeysuckle. The white admiral caterpillar begins its journey towards adulthood in late summer but then hibernates through the winter, resuming its growth the following year. A patch of oak or mixed woodland, with some flowering bramble and some honeysuckle, provides an ideal site at which to seek out this large and attractive butterfly. I have seen them at various sites across the county but tend to favour Holkham in the north and Knetishall Heath in the south, in part because of the other species they hold.

The purple hairstreak is a much smaller butterfly, darkly coloured and with a deep sheen that flashes purple when caught in the light. The species is associated with oak, though adults may sometimes be seen around ash, and they spend most of their time in the canopy feeding on honeydew or basking, wings open, in the sun. This arboreal association makes them difficult to see well but they can be watched through binoculars as they flit around the canopy, silhouetted against the summer sky. Populations have a colonial structure and numbers can vary greatly from one year to the next but it is worth putting in the effort to catch up with these delightful little butterflies.

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