Length ~ 6.0 mm. Orthotylus is a large genus of predominantly green bugs. Many are extremely similar and species identification based on external features is often difficult. The hostplant can be very informative.  O. flavinervis is one of the larger species and is found on Alder and Sycamore. The upper surface is covered in dense pale hairs, and the wing membrane is dusky, with yellow veins. The 1st antennal segment is brownish.

Orthotylus marginalis.

Unless identified by a recognised expert, a photo is required and the specimen should be examined with a microscope. In the comments box, state the key or ID method used and describe the size and identifying characters.

On Alder and Sycamore.

Adult: June-August

A locally common bug throughout England and Wales.

Rarely recorded in Leicestershire and Rutland.

https://www.britishbugs.org.uk/heteroptera/Miridae/orthotylus_flavinervis.html