Winter Gnat Trichocera spp.

The Winter Gnat, also called Winter Crane Fly, is a large, long-legged, non-biting gnat that is around all year but males gather together to attract females in late autumn and winter and are attracted to light. The name is given to several species of Trichocerid gnat, which are related to gnats and crane flies; these are most likely to be Trichocera annulata or T. regelationis. Thanks to Martin Starnes for the photos above, including those "bare-back riding" (his words) on a November moth in December.
P.S. The gnat is no threat to the moth. Like most other gnats and crane flies, the adults don't eat at all but some may drink some moisture or nectar.