Extracted from C. S. Sheffield 2011. Canadian Journal of Arthropod Identification No. 18 (November 2011)
Megachile (Chelostomoides) angelarum Cockerell, 1902
Megachile angelarum Cockerell, 1902. South. Calif. Acad. Sci. Bull. 1: 70 (♀).
Diagnosis. The female of M. angelarum can be recognized by the combination of the parallel sided metasoma, mandibles which lack cutting edges, and the complete apical white fasciae on T1-T5. They are most similar to M. campanulae. Females of M. campanulae lack the apical white fascia on T5. The male of M. angelarum can be recognized by the combination of three visible metasomal sterna, having 9-10 punctures between lateral ocelli and edge of vertex, the conspicuous front coxal spine, and T4 and T5 with conspicuous, very short and erect dark hairs. They are most similar to M. campanulae. Males of M. campanulae have only 4-5 punctures between lateral ocelli and edge of vertex, a reduced front coxal spine which is concealed by the dense, white pubescence, and T4 and T5 with conspicuous, long and erect pale hairs.
FEMALE: Length 10-11 mm.
Head. 1) compound eyes slightly converging below; lateral ocelli subequally distant from eyes and margin of vertex, 2) clypeal margin with a deep quadrate median emargination between two prominent tubercles, denticulate towards lateral margin, 3) mandibles distinctly 4-dentate, without cutting edge (Plate 1, Figure M3), 4) gena subequal to compound eye in width, 5) punctures of vertex coarse, deep and distinct, slightly and uniformly separated (<1 pd), those on gena not quite as coarse but considerably closer; frons quite coarsely and very closely punctate, fine and densely crowded on paraocular area, supraclypeal area with some narrow, shining spaces medially, but punctures coarse and deep, becoming very close laterally, clypeus very closely and coarsely punctate, becoming somewhat more finely and more obscurely so toward apical margin medially, 6) pubescence pale on head, rather short and sparse, whitish and somewhat more copious on face around antennae, on inner orbits and on gena below, becoming sparse on clypeus, gena above and on vertex where it is somewhat more yellowish, 7) F1 broader that long (1.5:1), about half as long as pedicel and subequal in length to F2, remaining flagellomeres subquadrate to very slightly longer than broad, apical flagellomere more elongate (3:2).
Mesosoma. 1) pubescence short, sparse and entirely white laterally and posteriorly, longer below and on lateral edges of propodeum, quite dense around pronotal lobes, very short, sparse and entirely pale on mesoscutum, whitish and somewhat more erect and elongate on scutellum, 2) mesoscutum and scutellum coarsely, deeply and closely punctate throughout, interspaces very narrow but shining, punctures somewhat more widely spaced on scutellum, finer and very close on axilla; pleura somewhat shining between coarse, deep and rather irregular punctures below, these becoming densely crowded anteriorly; propodeum somewhat smoother but dull, with fine, shallow punctures that are well spaced medially, triangle dull and impunctate, rugosostriate along basal margin, 3) all basitarsi somewhat narrower and shorter than their tibiae, spurs yellow, 4) tegula minutely and closely punctate, 5) wings hyaline basally, becoming faintly clouded apically, veins black.
Metasoma. 1) elongate and parallel-sided; T2-T4 with deep, transverse, basal grooves, largely filled with white tomentum, basal margins distinctly and sharply carinate, apical margins of terga depressed at extreme sides but not medially, the apical, white fasciae complete on T1-T5, though sometimes becoming narrow medially; T1 with rather thin, erect, pale pubescence, lateral angles densely white tomentose; discal pubescence of T2-T6 extremely sparse, entirely pale, hardly evident; T5 weakly grooved toward base but basal margin not at all distinct, and apical margin depressed only toward sides; tergal punctures quite deep and distinct, variable in size and spacing, rather coarse and sparse medially on each tergum, becoming somewhat closer laterally and toward apical margin, quite fine and close over most of T1, rather uniformly coarse and close on T5; T6 vertical, nearly straight in lateral view, with an abrupt, apical lip, largely covered with pale, subappressed hairs that obscure the surface slightly, 2) S6 covered with short scopal hairs that are pale toward base but become darker toward apex; scopal hairs otherwise yellowish-white, the sterna rather uniformly, closely, deeply and rather coarsely punctate, apical margins narrowly depressed and very narrowly hyaline.
MALE: Length 8-9 mm.
Head. 1) compound eyes very slightly convergent below; lateral ocelli subequally distant from eyes and margin of vertex, 2) clypeal margin with two tubercles on each side of mid-line; punctures of clypeus very coarse and contiguous, becoming somewhat finer and closer toward apical margin, 3) mandibles 3-dentate, lower process broadly triangular, median in position, 4) gena slightly narrower than compound eye (5:7), shallowly excavated just below base of mandible, 5) vertex shining, punctures small but coarse, deep and close, separated by less than 1 pd, with 9-10 punctures between lateral ocelli and edge of vertex, with a narrow impunctate area approximately 1 pd wide at upper edge of compound eye, punctures becoming slightly finer and closer on gena; frons coarsely and very closely and deeply punctate, becoming finely rugose laterally and over supraclypeal area, 6) pubescence of head mostly pale, rather short and sparse on gena and vertex, becoming quite copious and plumose around antennae and over lower part of face, largely hiding surface, longer on gena below, very dense and shorter on lower surface on mandible and lower process, vertex with very short, erect and scattered dark hairs, 7) F1 broader than long (1.5:1), slightly shorter than pedicel, about half as long as remaining flagellomeres, which are longer than broad(1.5:2), apical flagellomere more elongate (2:1).
Mesosoma. 1) pubescence rather short, sparse, entirely white laterally and posteriorly, quite dense around pronotal lobes, very short and sparse on mesoscutum, becoming somewhat more erect and elongate on scutellum, 2) punctures of mesoscutum coarse, deep and close, slightly separated over most of surface, but interspaces very much narrower than diameter of punctures, interspaces on scutellum somewhat more distinct (1 pd), but fine and very close on axilla; pleura below somewhat shining between coarse and deep punctures, the punctures becoming finer and closer above; propodeum laterally somewhat smoother but with very fine, shallow and close punctures, these becoming well spaced medially, face of triangle somewhat more velvety, impunctate, rugosostriate basally, 3) front coxal spine reduced, its height equal to basal width, not concealed by the short, white pubescence; front tarsus entirely dark, tarsomeres 1-3 moderately dilated and slightly concave below, with some elongate, pale brownish hairs along anterior margin, but the usual posterior fringe absent, a long cluster of intertwined setae at base of posterior margin of basitarsus; spurs yellow, ; mid and hind tarsi slender and simple, 4) tegula minutely and closely punctate, 5) wings subhyaline basally, becoming faintly clouded apically, veins black.
Metasoma. 1) T2-T5 deeply grooved across base, and with white fasciae, basal margins quite distinctly carinate, apical margins yellowish-hyaline, quite deeply depressed across entire width of terga, apical white fascia evident only toward extreme sides of T1, fasciae on T2 and T3 limited to a few hairs; T1 with rather copious, elongate, white pubescence, discal pubescence of T2-T3 very sparse and obscure, hardly evident, entirely pale, T4 and T5 with more conspicuous, very short and erect dark hairs; punctures deep, distinct and rather coarse, rather uniformly separated, interspaces not much exceeding diameter of punctures, these slightly coarser at extreme sides than in centre, T1 and T5 more finely and closely punctate, T6 with smaller punctures with no interspaces; T6 vertical with a rather dense, basal, white fascia, otherwise quite densely covered with short, suberect, dark tomentum, with a few more elongate, black hairs, carina very obscure, with a rounded median emargination, elevated but very slightly on each side above surface of tergum, median teeth of apical margin broadly carinate and very low, largely obscured by dense, white tomentum, very much nearer the acute, lateral teeth than to each other; T7 transverse, not at all produced medially, 2) S1- S3 exposed, S4 retracted, entirely hidden but unmodified; sterna quite closely and deeply punctate throughout, S2 and S3 somewhat swollen on each extreme side; apical margins depressed with dense, long, white pubescence, disc of S3 with white subappressed pubescence.
Discussion. This species is a cavity nester and can be trap-nested (Barthell et al. 1998; Frankie et al. 1998) (Table 1). Like other members of the subgenus it collects resins and gums for nest construction and thus lacks the cutting edges between the mandibular teeth (Michener 1962).
Distribution. Southern BC