Purple Hairstreak
Key facts
- Latin name
- Favonius quercus
- Family
- Lycaenidae
- Wingspan
- 26-35 mm
- Flight season
- July — August
- Host plants
- Pedunculate oak, Sessile oak
- Conservation status
- LC
Appearance
The purple hairstreak (Favonius quercus) is a small butterfly with a wingspan of 26–35 mm. In males the upper side is dark brown with a bright purple-blue sheen; females lack metallic gloss.
The underside is diagnostic: uniform gray-green with a fine white transverse band mimicking shadow on a leaf. At the lower end of the forewing is an orange spot with a thin white "tail" — a hallmark of the genus.
Range and habitat
Found in Europe and Asia Minor. In Russia in the European part where oaks grow.
Strictly tied to oak woods and mixed forest with oak. Butterflies live in the canopy and rarely descend below 5–6 m, which makes observation difficult.
Life cycle
One generation per year. Flight July–August.
Eggs are laid on the bark of young oak shoots at the base of buds. The egg overwinters. The caterpillar hatches in spring and feeds on opening buds and young oak leaves. The caterpillar is inconspicuous, brown, well hidden. It pupates in bark crevices.
Link to oak
The purple hairstreak is one of the few blues fully dependent on a single tree genus. Oak is host for caterpillars and a place for adults to roost and court. Loss of oak woodland directly affects this species.
Like other blues, caterpillars are tended by ants that guard them in exchange for sweet secretions.