Length 4 to 5 mm. Nysius senecionis has the 2nd antennal segment pale with a dark ring at the base and the wing membrane is usually clear and unmarked. It is separated from the very similar N. graminicola by the shorter 1st segment of the hind tarsus, which is less than the combined length of the 2nd and 3rd segments (including claws). In addition, the matt area of the metapleuron is extensive.

other Nysius, especially N graminicola

• Black basal ring to the 2nd antennal sement
• Extensive matt area to metapleuron
• Length of 1st hind tarsal segment greater than combined length of 2nd and.3rd segments and claws 

Detailed examination of the specimen is recommended; a field photograph may not be adequate because the key features are small or hidden.  Ensure the antennae, hind tarsi and the metapleuron are clearly visible in your photos.  Note habitat.

It is associated with a range of composites such as Ragwort and Fleabane.

Adult: All year.

Widely scattered (ref: British Heteroptera checklist 2021, on British Bugs website).  A fairly recent arrival in Britain, first recorded in 1992 and now widespread and common in much of southern Britain as far north as Yorkshire.

Occasionally recorded

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