Head: Black. Lower face has pale yellowish hairs, denser on inner eye margin. Male lower face has more dense whiter hairs.
Antenna: Black – females 10 segments, males 11.
Thorax: Black, all segments more or less outlined in pale yellow.
Collar (pronotum) yellow stripe not interrupted at centre.
Segment 1 (scutum) has 2 yellow longitudinal median lines each side of centre.
Segment 2 (scutellum) has black spines (axillae) at each side edge; not protruding.
Segment 3 (propodeum) has yellowish spots curving inward on each side.
Thorax sides have some yellowish hairs below wing bases, more so on male. Tubercles are faint reddish-brown surrounded with a yellow fringe of hairs. Underside of thorax dense silvery on male only.
Wings: Wing knobs (tegulae) reddish. Wings darkly tinted (lighter on male), tips darker.
Legs: Thighs (femora) blackish. Shins (tibiae), feet (tarsi) and spurs reddish. Hind leg colours darker on male.
Abdomen: Black with all pale yellow stripes either slightly indented or slightly interrupted at centre.
Segment 1 has a stripe at both the base and lower rim, and usually the 2 are joined at side edges.
Segment 5 female has a large spot on each side of centre.
Female tip is a triangular patch of silvery-white hairs.
Male has 1 to 6 striped and slightly interrupted at centre.
Underside of segments 2 to 4 striped.
Similar Species: E. canadensis has collar (pronotum) yellow stripe interrupted at centre. The two yellow median stripes on thorax segment 1 (scutum) are joined to become V-shaped. The lower stripe on abdomen segment 1 has a much wider gap than E. autumnalis and abdominal segment 5 is either continuous or with a slight gap at centre. On E. autumnalis segment 5 has a spot at each side. The differences on segment 5 can be very slight between the two species. Epeolus canadensis flies very late June to very early August. E. autumnalis flies only in September.
E. pusillus and E. scutellaris have red thighs (femora), not black.
Size: Female 9 to 11 mm. Male 7 to 9 mm.
Flight Time: September only.
Habitat: Forest edges and meadows.
Food: Adults eat nectar. The larva are cleptoparasites of Plasterer Bees Colletes mostly C. compactus.
Life Cycle: Females lay eggs in ground-nesting cells of Plasterer bees, Colletes compactus larva hatch and kill the Plasterer bee egg and feed on the provisions of pollen and nectar stored in the cell.
Comments: Essex County – Ojibway Prairies, Windsor. Sept 22, 2001 and 2002.
For information on synonyms, references and type specimens see next page