Adults are 6 to 7 mm long, fairly thick set, predominantly black, but with hind margins of the abdominal segments pale and with white marked legs.

Periclista lineolata larvae feed on sessile and English oak. This species has branched bristles dorsally with the branches about the same length as the stems. The anal segment has a row of six unbranched bristles with a small forked bristle on either side posterior to the row. The head is dark.

Adult, Larva and leafmine (when the host plant is identified)

Look in areas containing mature Oaks.

Springtime species usually seen about April.

The spiky looking larvae graze the undersides of the leaves of Oaks.

Most British records come from southern Britain

Fairly frequent in Leicestershire and Rutland.

https://www.sawflies.org.uk/periclista-lineolata/