The May highflyer (Hydriomena impluviata) is a moth of the family Geometridae. It is found across the Palearctic region and the Near East although its range is largely determined by the presence of its larval food plant. The species flies at night from May to July and is attracted to light. The larva feeds on the leaves of alder, spinning 2 leaves together so it can feed undisturbed. The species overwinters as a pupa under loose alder bark. 1. \n* The flight season refers to the British Isles. This may vary in other parts of the range.