Length 3-4mm. Dark pronotum, dorsal surface dull with a short pubescence. Usually brachypterous although fully-winged individuals do occur. 

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.

Summer-Autumn.

Unlike most ground bugs this species overwinters as eggs which hatch in the spring.

Widespread but local throughout the UK.

Uncommon.

https://www.britishbugs.org.uk/heteroptera/Lygaeidae/stygnocoris_rusticus.html