Common in woodland, heathland and fens throughout much of England, Wales and southern Scotland. In Hampshire and on the Isle of Wight often abundant in deciduous woodland, with the males often found swarming about the tips of branches of oak, sycamore and other deciduous trees. Wingspan 14-18 mm. Day-flying, males congregating in swarms in bright sunshine. Fairly unmistakable. Larva feeds on leaf litter, living within a movable case.