Oak marble gall wasp
The oak marble gall wasp is a tiny dark brown wasp, only about 2 millimetres long. It does something amazing: it makes oak trees grow round balls, like marbles, on their buds. Each ball is a cosy home for one baby wasp.
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Fun facts
The marble galls start green, then turn hard and brown, and can grow to about 2.5 centimetres across.
When the baby wasp is grown up, it chews a little round hole and flies out of its marble.
It needs two kinds of oak trees to finish its life story: one generation grows on common oaks and the next on Turkey oaks.
Birds, squirrels and mice sometimes crack open the galls to eat the larva inside.
Long ago, people used marble galls to make ink for writing and to dye cloth.
Most asked questions about Oak marble gall wasp
?What are the round balls on oak trees?
Often they are marble galls. The oak grows them around the egg of a tiny gall wasp, and one larva lives inside each.
?Why is it called a marble gall?
Because the gall it makes is hard, brown and round, just like a marble.
Myth buster
Myth: The round balls on oak trees are oak fruits or nuts.
Truth: No. They are galls, little homes the tree grows after a tiny wasp lays an egg in its bud. The real oak fruits are acorns.
For bug experts
- Scientific name
- Andricus kollari
- Group
- Wasps and hornets
- Family
- Cynipidae
- Classification
- Insecta > Hymenoptera > Cynipidae
- Lives on
- Europe
- Also known as
- Marble gall wasp
Where the facts come from
- Andricus kollari (Wikipedia, CC BY-SA 4.0): what it looks like, where it lives, what it eats, sizes and fun facts, retold in simple words.
- Picture by TristramBrelstaff. CC BY-SA 4.0, Wikimedia Commons. The round sticker of this bug is cut from the same picture.
If we got something wrong, sorry, we are bug fans, not a science journal. Tell us at [email protected] and we will fix it.
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