Drymus brunneus is a brown Seed Bug measuring 3.6 to 5.4 mm. It can be told apart from its family members, but you have to look carefully. The entire pronotum is brown. There are no long, erect hairs on the tibia (the shins) and the legs are mostly brown, not black. Also the wings are noticibly widened in the middle. So this species has a rather oblong shape, contrary to it's brothers which give a slimmer impression. Adults usually have shortened wings. It is rare to see a Drymus brunneus with fully developed wings.
The animal is often found in rather damp places, usually among leaflitter or mosses. They feed however by sucking on the seeds of trees or shrubs, such as birches and alder. It is single-brooded but breeding continues in all suitable seasons, so eggs, larvae and adults can be seen all year round. Adults are even active on mild winterdays. A common species all over Europe, including all of the British Isles and Ireland.