Osmia emarginata

Taxonomy

Family: Megachilidae
Subfamily: Megachilinae
Tribe: Osmiini
Genus: Osmia Panzer, 1806
Subgenus: O. (Osmia) Panzer, 1806
Species: Osmia emarginata Lepeletier, 1841
Common name: none

Overview

Osmia (Osmia) emarginata are black bees, sometimes with a metallic blue shimmer to the body (Amiet et al. 2004). Females have intermixed black and pale hairs on the face, yellow-white hair on the thorax, pale hair on T1–T3, both black and pale hair on T4, and primarily black hair on T5–T6. Male hair coloration is similar to the females except for the head, which is primarily white on the face and often has intermixed black and white hairs on the vertex. Female body length is 13–15 mm, and male body length is 10–12 mm (Banaszak and Romasenko 1998).

Diagnostic characteristics

(modified from Peters 1978; Banaszak and Romasenko 1998)

Mouthparts much smaller than the length of the entire body when extended.
Terga without apical hair bands.
Female clypeus with smooth apical margin that forms a wide median emargination that can be somewhat triangular-shaped.
Female clypeus without lateral horns.
Female with a distinct pit at the bottom of the eye, just behind the malar space.
Female mandibles are large, with acute, long lower teeth and wide cutting edge between inner teeth.
Female scopa red to reddish-yellow.
Male hind basitarsus with red or yellowish hair.
Male S6 without gradulus basally.
Male gonocoxite almost right-angled subapically.

May be confused with

Osmia emarginata is similar enough to O. mustelina that it could possibly be considered a subspecies of O. mustelina (Peters 1978). Females can be more easily distinguished by the shape of the apical margin of the clypeus and the absence of an impunctate median ridge on the disc of the clypeus (Banaszak and Romasenko 1998). Males are more difficult to distinguish; in general O. emarginata has fuller, reddish-brown hair on the thorax, the gonocoxite is almost right-angled subapically, and the ventral ridge is more apparent (Peters 1978).

Phenology

Osmia emarginata adults have been recorded in flight from May to July (Banaszak and Romasenko 1998).

Host associations

Osmia emarginata are polylectic and have been associated with Fabaceae, Boraginaceae, Cistaceae, Scabiosa (Caprifoliaceae), and Ajuga (Lamiaceae) (Amiet et al. 2004).

Nesting behavior

Osmia emarginata are known to nest in fissures between stones and cavities in rock, more often in broad cavities than narrow ones (Banaszak and Romasenko 1998). Nest cells are arranged in an irregular, clump-like shape (Banaszak and Romasenko, 1998). Nest cells are composed from chewed leaves (Amiet et al. 2004).