Spangle galls are disc shape galls created by a tiny wasp.
The larvae feeds on the tissue of the leaf while creating little damage, the oak leaf can host up to 100 galls. It falls to the ground in autumn, (this is when we notice them most) but continue to grow before emerging as adult in April. These tiny wasps have both A sexual and bisexual generations. The females then lay their eggs in the oak catkins in June creating a round 'currant gall' where the bisexual generation emerge and start the cycle again.