Apterae of Aphis viburni are slate-coloured, brownish green or dark brown, sometimes with paired pleural wax spots on the abdomen. Of all the 'black aphid' group, A. viburni is probably the most variable in colour.

Aphis viburni can most readily be distinguished from A. fabae (which can also use Guelder-rose as a primary host) by the gall like gathering of strongly curled leaves (see pictures) that it produces. A. fabae does not produce a gall. The gall provides shelter for both the aphids and attendant ants.

Best recorded when present in a gall-like gathering of leaves on Guelder-rose.

Where Guelder-rose is present.

Late spring and summer.

True status in Britain is difficult to determine due to lack of records.

Status in Leicestershire and Rutland not known.

https://influentialpoints.com/Gallery/Aphis_viburni_viburnum_aphid.htm