Reprinted with permission from: Mitchell, T.B. 1962 Bees of the Eastern United States. North Carolina Agricultural Experiment Station Technical Bulletin No. 152.|
FEMALE — Length 11 mm.; entirely black, without metallic reflections; length of face only slightly greater than distance between eyes above; eyes very slightly convergent below; lateral ocelli somewhat nearer eyes than to margin of vertex, much nearer each other; clypeus strongly convex, considerably produced apically, margin strongly thickened, very slightly outcurved, but not otherwise modified; median length of labrum about equal to basal width; mandibles not much broadened apically, rather short, distinctly 4-dentate (fig. 32); cheeks more than double width of eyes; wings lightly infuscated, not much darker apically, 2nd recurrent vein reaching 2nd submarginal cell much nearer apex than 1st does to base; tarsal segments simple and unmodified, mid and hind spurs piceous; pubescence largely pale over head, thorax and basal abdominal tergum, with a few blackish hairs behind eyes and some obscure fuscous hairs intermixed on clypeus, rather short on head but quite dense over front of face, quite elongate and copious on thorax, legs largely black pubescent; scopa entirely black, discs of abdominal terga 2-5 with rather short but erect and conspicuous pubescence, becoming more elongate toward sides, largely pale on tergum 2, with a few dark hairs intermixed, becoming more blackish on the following terga, entirely pale and largely subappressed on tergum 6; punctures rather fine and close in general, close but not crowded on vertex medially, becoming somewhat more distinctly separated but close laterally and on upper cheeks, becoming more crowded on cheeks below, median area between ocelli and antennae densely and finely rugose, rather shallow and sparse on each side of clypeus, but clypeus densely rugose; punctures fine and densely crowded over most of scutum, becoming slightly separated only in center of disc, very fine and close on scutellum, crowded only along posterior margin; pleura dull, punctures fine and very close in general, lateral faces of propodeum smooth but dull, posterior face more tessellate, punctures very minute and obscure, dorsal area velvety, not at all striate along upper margin; abdominal terga somewhat more shining, punctures very fine, rather close but distinctly separated, those in center of each disc becoming minute and rather sparse toward apical margin, these rather broadly but slightly depressed, with minute and sparse punctures; tergum 6 with exceedingly minute, close and evenly distributed punctures.
MALE — Length 10-11 mm.; entirely black, with no metallic reflections; face slightly longer than distance between eyes above; eyes slightly convergent below; lateral ocelli slightly nearer each other than to eyes, subequally distant from eyes and margin of vertex; clypeus rather broadly convex, apical margin considerably produced, median area nearly straight; median length of labrum slightly greater than basal width; mandibles bi-dentate; cheeks much broader than eyes; wings subhyaline, 2nd recurrent vein reaching 2nd submarginal cell slightly nearer apex than 1st does to base; mid tarsal segments slender and simple, hind basitarsus slender at base and broadly dilated toward apex, not tuberculate, mid and hind spurs piceous; pubescence whitish or pale ochraceous over most of head and thorax, rather dense on front of face, clypeus and lower cheeks, on pleura and around margin of dorsum of thorax, largely pale on legs, whitish on basal abdominal tergum, short, suberect and somewhat darker on discs of the following terga; punctures deep, distinct, rather coarse and close on head and thorax, but fine and densely crowded on clypeus, finer and very close on cheeks below, minute and slightly separated on abdominal terga 2-5, somewhat coarser, but shallow and rather close on basal tergum, more widely separated on 6, apical margins rather broadly depressed, with scattered minute punctures; sternum 2 broadly subtriangular apically, only partially covering sternum 3, this with a rather broad, median emarginate area which is largely occupied by convergent setae; sternum 4 somewhat produced, median third sub- truncate; tergum 6 without a distinct, median emargination; tergum 7 very shallowly emarginate medially; sterna 5-8 entirely retracted, apical margin of 6 with a median truncate lobe (much as in simillima, fig. 28); apex of gonocoxite similar to that in felti (fig. 31).
DISTRIBUTION — This species is holarctic and is recorded on this continent in Alaska, across Canada and in the Northwestern and Rocky Mountain states. Although it has not yet been recorded from any of the eastern states, it has been collected in Minnesota and Ontario, and it seems possible that it will eventually be found in some of the border states in the Northeast. In the Catalog of Hymenoptera (p. 1165) Osmia xanthomelaena Smith is included in the synonymy of nigriventris. It was described by Smith in 1844 (Zoologist 2, p. 745) but was attributed to Kirby. However, the name xanthomelaena was first proposed by Illiger (Magaz. f. Insectenk. 5, 1806, p. 112) and is included in the synonymy of Osmica fuciformis by Dalla Torre (Cat. Hym. p. 395). Specimens from Smith’s collection were found in the Hope Museum at Oxford, and it is my opinion that they do not represent nigriventris. A need for more study of the Palaearctic species in this group is indicated.
Extracted from: Molly G. Rightmyer1, Terry Griswold1, Michael S. Arduser. 2010. A review of the non-metallic Osmia (Melanosmia) found in North America, with additional notes on palearctic Melanosmia (Hymenoptera, Megachilidae) ZooKeys 60: 37–77|
Diagnosis. Females of this species are known by the swollen clypeal margin (Figs 11, 12) (approaching the extreme look found in O. bucephala, but unlike in that species, there is no metallic coloration in the integument of the meso- and metasomata). Males are known by the strongly refl exed apicolateral angles of T5 and T6 (Fig. 53). Unlike in O. bucephala, the midleg tarsal segments 2–4 are not modifi ed or swollen, and S2 is unmodifi ed (S2 of O. bucephala with a low tumescence bordered anteriorly and laterally by several rows of erect bristles).
Distribution. In the Nearctic, O. nigriventris is known from Oregon, Idaho, Wyoming, and Michigan north to Yukon and the Northwest Territories, east across Canada to Ontario, Quebec, and Newfoundland. In the Palearctic, O. nigriventris is known from France, Italy, and Slovakia north to Norway, Sweden, and Finland and east to Mongolia, northern China, and through Russia to Far Eastern Siberia (Müller 2010).
Comments. Osmia nigriventris is polylectic, with preference for Vaccinium (Ericaceae); it nests in old insect burrows in dead wood and constructs cell partitions and nest plugs with chewed leaves (Müller 2010 and references therein).