Length about 4 mm. The Psallus group includes many small bugs (< 6 mm) which are often mottled red, grey or dark brown. The pronotum and forewings are covered in scale like pale hairs and the tibial spines arise from black spots. Species identification of Psallus based on external features is often difficult and frequently impossible. Identification is complex and ideally requires microscopic examination. The images placed in red boxes are likely to be this species but they can only be claimed to be representative of the species. However, the host plant can be informative and may narrow down the range of possibilities.

Detailed examination of the specimen is needed to identify the species.

Several very similar Psallus species occur on Oak, one of which is P. varians.

Adult: May-August.

The adults and larvae feeding on small insects as well as the host trees. 

very common (British Heteroptera checklist (2021) - https://www.britishbugs.org.uk/systematic_het.html 

Common in Leicestershire & Rutland.