Identification: Black area on abdominal segment 1 is small, sub-triangular. Stripes medium yellow, fading to white on last few abdominal segments. Median lines on thorax touch collar. Female abdomen tip mostly bare.
Head: Black with yellowish hairs around antenna bases on female. Male face covered with yellow hair. Lower face (clypeus) has no center longitudinal ridge.
Antenna: Black; base (scape) and segment 1 may have some reddish-brown to orange.
Thorax: Black with thin, intermittent yellow lines around all segments. Collar has thick yellowish pile. Segment 1 (scutum) has two yellow median stripes, one on each side of an indented center line. These stripes touch the collar (lines widen on male). Segment 2 (scutellum) has long slender tooth (axillae) at each side edge. Segment 3 (propodeum) has line of hairs along outside edges. Thorax side has dark tubercle with yellow fringe. Under tubercle is another crescent or lunate mark. Tufts of hair behind and below wing bases. No yellow hair on underside.
Wings: Wings evenly tinted; not darker at tips. Veins dark.
Legs: Thighs (femora) dark, tips light. Shins (tibiae) and feet reddish-brown, infused with dark streaks. Spurs dark. Underside of legs may have yellowish pile.
Abdomen: Black with yellow stripes, colorr fades on last few segments.
Segment 1 has two stripes; the side thickly joined together. Centre black area is small and sub-triangular. Both stripes are slightly interrupted at centre.
Segment 2 stripe complete across segment; small mark above stripe at each side edge is squarish; smaller or absent on male.
Segment 3 stripe complete across segment.
Segment 4 stripe also compete, but paler.
Female segment 5 has only scattered whitish hairs. No white crescent. Tip indented (concave), squared. Underside dark, rarely with some white pile on sides of 2 and 3, but no stripes.
Male segment 5 stripe is narrow, whitish, continuous across segment. Segment 6 (male) usually without stripe, but may have a small white dash at centre. Underside of segments dark, rarely with some white pile on sides of 2 and 3, but no stripes. Segment 4 has fringe of long brown curved hairs. Segment 5 has only very short brown hair.
Similar Species: On Triepeolus lunatus – thorax mid stripes do not touch collar, underside of abdominal segments 2 to 4 are striped, clypeus has a ridged mid-line and the female has a crescent on abdomen tip.
Size: Female 13 mm. Male 12 mm.
Habitat: Forest edges and meadows.
Food: Adults feed on pollen and nectar.
Flight Time: July and August
Life Cycle: Larvae are cleptoparasites of Digger or Long-horned bees Melissodes species. Listed as a possible parasite of Melissodes communis which does not fly in Ontario. See Comments.
Comments: Triepeolus simplex flies only in Ontario in Canada. Niagara region per Cordero thesis from Brock University. Essex County (my photos). Also in Michigan.
T. simplex is uncommon in Wheatley: once in 2009 and twice in August of 2013. It might be a parasite of Melissodes subillata, another rare one that showed up in August of 2013, but this is just a guess.
For information on synonyms, references and type specimens see next page