Epeolus are cuckoo bee that attack only Plasterer Bees Colletes species. Females sneak into Colletes ground nests, and lay an egg between the two cellophane layers surrounding each cell. When the Epeolus larva hatches, it first finds the Colletes egg or larva and kills it by using its long mandibles. Then it feeds on the stored pollen/nectar mixture.
In general Epeolus have black faces with varying amounts of hair. No yellow on male faces, but usually they have more hair than the females. Females have 10 antenna segments, males have 11. Females have 5 visible abdominal segments, males have 6.
All have narrow cheeks (genae), and collar (prothorax) which extend to the tubercle on the thorax side.
Thorax and abdomen have white to pale yellow markings. All (except E. bifasciatus) have two mid stripes extending half-way down the thorax from the collar. Slight variations in these stripes are main ID marks for some Epeolus.
Thorax segment 2 (scutellum) is slightly raised, rough with arrow-like points projecting from the sides (axillae). Varying amounts of red on the scutellum are also main ID marks.
Except for E. bifasciatus, all have stripes on each segment of the abdomen, and the first segment has two stripes with a black area between them.
Epeolus are difficult to tell from Triepeolus. Triepeolus are usually larger. Females lack the bright white spot at abdomen tip which is present in most Epeolus.
Eight Epeolus regularly fly in Ontario. Two others are doubtful (E. ilicis and E. interruptus).
Epeolus americanus (lanhami) – Rainy River; Sudbury
Epeolus minimus – Toronto to Rainy River
Epeolus ilicis – cannot be verified in Canada
Epeolus interruptus – One verified in Ottawa 1947
Epeolus autumnalis – Essex County up to Toronto – Sudbury
Epeolus bifasciatus – Widespread in Ontario
Epeolus canadensis – Essex County up to Georgian Bay – Ottawa
Epeolus lectoides – Essex County up to Toronto
Epeolus pusillus – Rare – Essex County to Grand Bend – Ottawa
Epeolus scutellaris – Widespread in Ontario.