Length 4-5mm. A bright green leafhopper, small than others in this subfamily, with the scutellum and inner margins of the wings dark reddish-brown. The antennae are long.

Other Idiocerinae on poplars

Good photographs of a specmen required; from top, side and face; note host plant

On grey and white poplar. Overwinters on evergreens, particularly Yew.

All year. 

A fairly recent incomer to the UK, spreading north.   Common (ref.: UK Auchenorrhyncha checklist 2021)

Uncommon. 

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