Length 5-6mm, and associated with Acer spp. esepcially Sycamore and Field Maple. Forewings marbled greyish/reddish brown, with a hyaline apical part and a light spot on the clavus.  Extremely similar to the closely-related Acericerus vittifrons - females of these species cannot be separated, males can be distinguished by the short dark bar on the face with a pale midline, which does not reach the ocelli (the minute simple eyes between the large compound eyes).

Acericerus vittifrons and A heydenii are very similar and also found on Acer spp.

Good photographs clearly showing an overall view and the vertex (face) of the male required. 

Acer, especially Sycamore and Field Maple

Autumn-Winter.

First recorded in Britain in 2007, now spreading from the south-east.

Uncommon

https://www.britishbugs.org.uk/homoptera/Cicadellidae/Idiocerus_ribauti.html