The purple hairstreak (Favonius quercus) is a butterfly in the family Lycaenidae distributed throughout much of Europe,[2] North Africa, Anatolia, Caucasia, and Transcaucasia.

Underside leaden-grey, with a proximally dark-edged white line before the outer third and in the anal area of the hindwing weak yellow spots.

Adult yellowish brown with a reddish tint, on the back a row of triangles connected by a dark line, the sides greenish.

The butterflies occur from June till August everywhere in the plains and hills, but usually singly, in certain years more plentifully.

[4] This active little butterfly is most often seen fluttering around high up in oak trees on warm sunny July and early August days.

In Ireland it occurs in a few isolated colonies scattered across the country but is probably still under recorded due to its reclusive habits.

Both sexes feed mainly on honeydew although females are occasionally attracted to flowers whilst taking a break from egg laying.

The caterpillar is fully developed inside the egg after two or three weeks but doesn't hatch until the spring whereupon it burrows into the flower buds to feed safely concealed.

Pupation usually takes place in the leaf litter where it is tended by ants who bury them, but also sometimes in a crevice in the bark of the foodplant.