The Green Hairstreak is a fast-flying little butterfly. Size 22-26 mm. Sexes are largely similar. Upperside is brown but almost never seen other than in flight - it only shows the green underside when resting. The Green Hairstreak is one of the earliest to appear in spring after the Small Tortoiseshell. It usually flies from early/mid May to late June (sometimes quite a bit into July) and is common in my area.