About Bromius obscurus (Linnaeus, 1758)
Bromius obscurus (Linnaeus, 1758) adults are typically black in overall color, and are covered in dull yellow-grey hairs. Their elytra and tibiae may be either black or reddish-brown, while the basal four segments of their antennae are orange-red. Adult body length ranges from 5.0 to 6.0 mm. Several distinct variations of this species have been formally described: the typical form has black elytra covered by whitish hairs; var. weisei (Heyden, 1883) has black elytra, yellowish hairs, and reddish brown tibiae at the base; var. epilobii (Weise, 1882) has brown elytra and tibiae, with whitish hairs; var. villosulus (Schrank, 1781) has brown elytra and yellowish hairs.
Historically, there has been scientific disagreement over whether the obscurus and villosulus forms represent two separate species, based on observed morphological differences as well as differences in habitat and food plant range. More recent authors have variously treated these two forms as either variations of B. obscurus, or separate subspecies of B. obscurus. The villosulus variation is superficially similar to the Korean species Aoria rufotestacea. In 2014, researchers found that almost all Korean specimens previously identified as Bromius obscurus were actually Aoria rufotestacea.
B. obscurus is a widespread species found across the Holarctic realm. In North America, it is distributed across Canada, ranging south to North Carolina in the eastern part of the continent and to California in the west. In Asia, it is one of the few eumolpine species recorded from northern Siberia. In the United Kingdom, B. obscurus was historically only known from a single 10 km2 square on the border of Cheshire and Staffordshire, near the Bosley area. No specimens have been recorded in this area since 1992. A 2014 report noted that the species had just been discovered at a single site in Scotland, which remains the only confirmed current location for B. obscurus in the United Kingdom.
