Favonius quercus (Linnaeus, 1758)

Host plants:
The larva feeds on oak species such as Quercus robur, Quercus pubescens or Q. petraea. In the south (e.g. Greece), I also observed larvae on Quercus coccifera and Quercus frainetto. Finally, I tapped them from Quercus ilex in Sardinia. The larva usually lives on older, blooming trees and in contrast to Satyrium ilicis hardly on younger, small bushes.

But obviously rarely also other trees than oaks are used for oviposition. In winter 2022/2023 I recorded several eggs on a Pyrus communis tree in an orchard meadow at least 150m away from the next oak in Stuttgart (S-Germany).

Habitat:
Favonius quercus inhabits oak forests of all kinds, grasslands with individual oaks etc. Favonius quercus is found even in urban areas if some older oaks are present.

Life cycle:
The caterpillar overwinters in the egg shell. The eggs are often found on the base of buds on the tip of the twig. Favonius quercus is usually ovipositing on tall oaks and only rarely also on higher growing oak scrub. The caterpillar is fully-grown after only three larval moults in May or early June, and the butterflies fly from June to August.

Endangerment: regionally endangered or decreasing

Endangerment factors:
Favonius quercus is locally in slight decline due to conversion of oak-rich forests into spruce, maple or beech monocultures. Nevertheless, it is in many regions one of the most common butterfly species, if appropriate detection methods are used (searching for eggs, tapping larvae with a stick).

Remarks:
The imagines are most likely to be observed near the ground in the morning. They usually live high up in the trees and feed on aphid sugar on leaves.

Favonius quercus occurs throughout most of Europe (except the oak-free northern and central Scandinavia), North Africa and wide parts of temperate Asia to Kazakhstan.