Wagner states that "there are no adult characters (including genitalia) that can be used to reliably separate the adults of the Red-crossed Button Slug from those of the Abbreviated Button Slug."
He suggests that the two may in fact be the same species. Adults with more faintly patterned wings are considered here to be the Red-crossed Button Slug.
IRWS, Topsfield, MA
https://www.inaturalist.org/observations/265980760