Length 11 to 15 mm. The female is an all black sawfly with very distinctive red legs except for the the apical part of the femora and the tarsi of the hind legs which are black. The male has a reddish area on the abdomen. The mouthparts are creamy white. The wing stigma is black.

Seen on umbellifers or flowering hedgerows.

June to August.

Widespread and probably fairly frequent in Britain, though not well recorded.

Rare or under recorded in Leicestershire and Rutland, the Ratby record of 5th June 2014 may be the first record of this species in VC55.

https://www.sawflies.org.uk/tenthredo-atra/