Last modified: March 14, 2021, 6:22 p.m.
A common species in the northern part of Belgium, elsewhere uncommon.
Larva lives in the fruits or seeds (acorns, nuts) of the host plant. When full grown, it leaves its feeding place. Hibernates as a larva in a cocoon in the soil. Pupation next spring or summer. Infected acorns show little evidence of the larval presence but are more 'squeezable' than normal ones, due to the activities of the larva which fills the created cavities inside the acorn with soft frass. Pupation in a cocoon in the soil. Adults come to light.
The adults fly in one generation a year; from June to August.