Adult apterae of Uroleucon obscurum are reddish brown to bronze with black antennae and siphunculi and a yellow cauda. The body length of an adult Uroleucon obscurum aptera is rather less than for most species at 1.8 to 3.7 mm.

Please provide close up images to support your record and state the host plant species.

Where Hieracium species occur.

Sexual forms appear in September, and the species overwinters in the egg stage

Uroleucon obscurum has been recorded on 26 Hieracium species. The species does not host alternate. It can be found on the upper parts of stems of Hawkweeds (Hieracium spp.).

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

Rarely recorded in Leicestershire and Rutland.

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