Where to see
Habitat: Mainly found in oak trees: sometimes single trees, but more often woods.
Caterpillar foodplants: Various species of oak tree, including native and introduced varieties.
Best places: Alner's Gorse Butterfly Reserve, where there is a large Alder Buckthorn which attracts the Purple Hairsteak to come low enough to photograph. Also Lydlinch, Moors Valley Country Park, and Motcombe Meadows.
When to see
Mainly July, but can be seen in the months either side.
Sightings by month (last 5 years)*:
Sightings this year*:
Most of the photos of the Purple Hairstreak here are a little misleading: they make it look an easy-to-spot and impressive butterfly, while in reality it is small and often just glimpsed. The first picture below gives you a better idea how how it is usually looks closer to, when it comes down to bask or sometimes feed on Bramble, Hemp Agrimony or umbillerfers such as Hogweed and Angelica.
Often you will only spot the Purple Hairstreak as “silver specks tumbling in the sky above the treetops” (A lovely quote from Dr Jeremy Thomas), a sight you may more readily see in the early evening. More rarely, they may be seen in the early morning especially after periods of rainy weather, when freshly emerged adults from chrysalises in ant nests can be seen close to ground level.
The male and female have similar underwings: grey with a jagged white streak and a purple spot with a black eye near the tail. All the Hairstreaks have small tails to the hind wings.
The upperwings are different. The male is purple all over except for the margins of the wings, though this is only picked up when the butterfly catches the light at the right angle. The female is brown, with a prominent purple splash, visible even in poor light.
*Note: The charts shown on this page are drawn only from casual sightings submitted to this website. Records from this website will be added to a lot more data collected throughout the year and used to compile the five-yearly Butterfly Atlases for Dorset and the UK.