Synonyms and other taxonomic changes
Smaller than E. scutellaris
Female 9 mm, male 7 to 8 mm.
Similar to the larger E. scutellaris but with less red in the scutellum/axillae and females lacking the strong median scutellar groove of scutellaris. The pseudopygidial hairs differ (broader in scutellaris, longer in pusillus). Males have pale hairs covering the entire sides of the thorax whereas in scutellaris there are conspicuous bare patches.
Male and female similar. Thorax segment 2 (scutellum) is black with reddish points on each side (axillae). Abdomen tip is orange on male. Spurs on mid and hind legs dark.
Head: Black with dense yellowish-white hair around antenna bases and also covering lower face on male; upper face hair sparse, more yellow. Cheeks very narrow, less than a 1/3 of eye width; covered with very short white hair. Mandibles brownish-yellow, reddish tips.
Antenna: Base (scape) black on top side, brownish-yellow on underside. Antenna long on female, short and stout on male. Segments dark brown on top side; underside of segments 1 to 3 reddish, rest yellowish-brown.
Thorax: Black, dull, very rough; all segments have yellowish hair at edges. Collar pale yellowish. Segment 1 (scutum) has 2 short longitudinal stripes, one each side of center. Segment 2 (scutellum) black with only a very slight median depression or indent; side projections (axillae) reddish-brown. Segment 3 (propodeum) side edges covered with dense yellowish hair, becoming dense under wing bases. Thorax sides entirely covered with dense yellowish hairs; on males hair is silvery. Tubercles reddish-brown, with yellowish fringe.
Wings: Wing knobs (tegulae) reddish-brown to brownish-yellow. Wings clear at base, becoming faintly darkened at tip, veins brown.
Legs: Legs are all reddish-brown to brownish-yellow covered with silvery pile. Thighs (femora) more red on female. All spurs dark.
Abdomen: Black, short with yellowish-white stripes either slightly interrupted at center or entire.
Segment 1 has two yellowish-white stripes connected at side edges. Lower stripe narrows slightly at center on female, may be very slightly interrupted on male.
Segment 2 stripe also narrows slightly at center on both female and male. Gray patch may be present above stripe at each side of segment.
Segments 3 and 4 stripes entire and not narrowing at center.
Segment 5 has two oval patches very close to each other near center on female; entire stripe on male. Segment 6 stripe entire on male.
Female tip is very short, silvery. Male tip as wide as long, reddish-orange with a few short hairs.
Underside of segment 2 may be reddish. Underside of 2 to 4 (2 to 5 in male) have entire white stripes.
Wyoming and Texas to Maine and Florida.
Forest edges and meadows.
The Hosts section on its Discover Life species page
lists known floral associations based on specimen records and images.
Hosts are Colletes compactus, C. americanus, C. ciliatoides and C. deserticola.
The female finds Plasterer bee nests, enters and lays an egg. When larva hatch, it kills the Plasterer bee egg, and feeds on the stored pollen, nectar.
Widespread but usually less common than E. scutellaris in the northeastern USA.
Holotype female by Cresson, 1874. #9204193. Locality: Massachusetts. In Smithsonian, no photos.
Lectotype: #2228 with right antenna off beyond joint three. In Academy of Natural Sciences ANSP – Drexel University, Philadelphia.
Note: Specimen in Museum of Natural History, University of Michigan.
Similar Species: E. scutellaris has lower thorax sides bare, abdominal stripes on segment 1 are not connected; underside of abdomen is shiny and without white stripes. Female thorax segment 2 (scutellum) is entirely red in E. scutellaris.
Proceedings of the Entomological Society of Philadelphia, 1864, Vol. 2 pp. 398 -399 by Cresson female.
Entomological News, 1892, Vol. 3, pg. 29 by Fox, male.
Transactions of the Academy of Science of St. Louis, 1898, Vol. 8, pg. 82 by Robertson.
Canadian Entomologist, 1903, Vol. 35, pp. 287 to 288. Keys by Robertson.
Entomological News, 1903, Vol. 14: Studies of Texan Bees by Brues - keys.
American Museum Novitates, 1921, #23: Epeoline Bees of the American Museum Rocky Mountain Expeditions by Cockerell, keys including Triepeolus pp. 13 to 15.
Psyche, 1926, Vol. 33, pg. 116: Phenology of Inquiline and Nest-making Bees by Robertson.
Entomological News, 1934, Vol. 45 #2, pg. 29 by Cockerell.
North Carolina Agricultural Experiment Station Technical Bulletin, 1962 #152. Bees of the Eastern United States by Mitchell.
American Museum Novitates, 1966, #2244: Larvae of Anthophoridae, Pt. 2 by Rosen:Larva Description, pp. 19 to 20.
Journal of the New York Entomological Society, 1968, Vol. 76 #2: Biological Notes on Colletes compactus and its Cuckoo Bee, Epeolus pusillus, pp. 106-111 by Rozen & Favreau.
American Museum Novitates, 1989, #2957 by Rozen: Morphology and Systematic Significance of First Instars of the Cleptoparasitic Bee Tribe Epeolini by Rozen 19 pp.
Journal Entomological Society Ontario, 2004, Vol. 135, pp. 88 to 89 by Romankova - keys.
Canadian Entomologist, 2006, Vol. 138 #2: Changes in the bee fauna (Hymenoptera: Apoidea) of an old field site in southern Ontario, revisited after 34 years: Table 1, pg. 156 by Grixti and Packer: [I]Epeolus pusillus]/I] present: 5 in 1968, 4 in 1969; none present during re-study in 2002 or 2003.