A large (20 to 28 mm) yellow and brown species very similar to Cimbex connatus. However, C. luteus has significantly more yellow on the body and the thorax is generally a lighter orange colour. Mature larvae are yellow rather than the yellow-green of connatus.

Cimbex connatus which has the basal three tergites mainly black, whereas these are mainly yellow in C. luteus.

Unless identified by a recognised expert, a photo is required. If the photo doesn't show the key ID features then in the comments box describe the size and identifying characters you have observed. If recording the larva please state whether it was found on Alder or Willow.

Where Alders and Willows, the larval food plants occur.

Adult: May to July

Larvae feed on Alders and Willows.

Widespread in England, but very infrequent.

Rarely recorded in Leicestershire and Rutland.

https://www.sawflies.org.uk/cimbex-luteus/