Silk Button Gall Wasp - Neuroterus numismalis

Neuroterus numismalis is a gall wasp that has two generations per year.

The agamic generation causes Silk Button Galls on the underside of Oak leaves. These are small, and thick, with a deep central depression.  They can be extremely abundant.

The sexual generation causes circular Blister Galls on Oak leaves, visible on both side of the leaf; green at first then brown.  The blister has radiating lines from the centre, and the exit hole is in either upper or lower surface.  

Agamic Gall Sexual Gall Adult

Around Oak.

Wasps emerge from the Silk Button galls from February to April.

The Silk Button Galls are abundant on the underside of the Oak leaves and can reach 3 mm across. This gall holds the agamic generation and looks like a thick, rolled edge disk with a deep central pit and gold hairs, there is no mark on the top of the leaf. It is a single cell gall holding one wasp and can be seen from August to October, until the leaves fall in autumn. The wasp larva will mature in August but remain in the gall on the ground throughout the winter, emerging the following year from February to April.

Common and widespread in Britain.

Common in Leicestershire and Rutland.