5-6.5mm. A largely black and orange sawfly with dark tinted wings. The head and thorax are black with orange on the tegulae, metapleura and the posterior of the mesopleuron. The abdomen is orange but with the apical tergites blackened to some extent. Legs are orange with infuscated tarsi.

This species has a red ID rating and unless identified by a known expert you must provide a satisfactory explanation of how it was identified for the record to be accepted.

Well vegetated areas, especially where Common Cleavers or other Galium species are present.

Best from May to August.

The larvae feed on various Galium species.

Widespread and thought to be fairly frequent in England and Wales.

Status in Leicestershire and Rutland not known.

https://www.sawflies.org.uk/halidamia-affinis/