Family Philodromidae (Running crab spiders)
Body length 4-5 mm.
The sexes vary quite differently, hence the scientific name. The male is black or dark brown with white edges, the female more beige in colour.
It is normally found on the lower branches of trees and shrubs in wooded areas, but it is also found in gardens and occasionally indoors. Seen spring to autumn. It is quite common in Southern Britain.