This longhorn measures about 15mm in length.  It is uniformly grey-black in colour, sometimes slightly bronzy and with punctured elytra.

Good photographs required. This species is rare in our area so it is best to retain a specimen until identification is confirmed.

The typical habitat is open mixed woodland and parkland where the hosts, which include a range of deciduous trees but more especially lime, are present in various stages of growth and decay.

Adults occur from May until July, they are active in warm weather and may be observed feeding on host foliage or, more rarely, various flowers in bright sun.

Life cycle: 1 - 2 years.  The S. dubia larvae develop in dead thicker twigs, branches and slender stems (up to 20 cm in diameter) of deciduous trees (Tilia cordata is a preferred host, but often can be found in other deciduous trees).

Very local across England north to the Scottish border and with a few widely scattered records from Wales.

Rare in Leicestershire and Rutland - the record from Willesley Wood in May 2022 is the first from VC55 for well over 100 years.