Bug FAQCola Nut Gall Wasp
Andricus lignicola · Order: Hymenoptera · Family: Cynipidae
Also called: Cola-Nut Gall
Cola-nut gall wasps make hard, firm galls up to about 10 × 8 mm on oak buds, and a small circular hole appears when the adult emerges. They are common on pedunculate and sessile oak across continental Europe from Great Britain to Asia Minor and cause no measurable harm.
Source: Wikipedia
How to recognize it
The gall is hard and firm, and after the adult leaves a small circular hole remains.
Source: Wikipedia
Size
Galls grow to roughly 10 mm long by 8 mm wide.
Source: Wikipedia
Is it a pest in the house?
Even when many are present, they cause no measurable harm.
Source: Wikipedia
What it eats
The female lays a single egg inside a leaf bud using her ovipositor.
Source: Wikipedia
When you see it
Adults appear in early summer following gall inception.
Source: Wikipedia
Where it comes from
The species is well known throughout continental Europe, from Great Britain to Asia Minor.
Source: Wikipedia
Lookalikes
The bisexual-generation gall looks very similar to that of Andricus kollari.
Source: Wikipedia
More photos
Questions people ask
How do I get rid of cola-nut gall wasps?
Remove and destroy the galls before they dry and the adults emerge.
Source: Wikipedia
What trees do they affect?
They form galls on the buds of pedunculate oak and sessile oak.
Source: Wikipedia
Are they harmful to my garden or house?
They cause no measurable harm even when present in large numbers.
Source: Wikipedia
Same family (Cynipidae)
Sources
- Wikipedia: https://en.wikipedia.org/wiki/Andricus_lignicola
Look it up elsewhere: GBIF · iNaturalist · BugGuide · Wikipedia
Text written 2026-10-24 from the sources above and checked sentence by sentence against them. Data fetched 2026-10-22.