Extracted from: Sheffield C. S., et al (2011). Leaf cutter and Mason Bees of the Genus Megachile Latreille (Hymenoptera; Megachilidae) in Canada and Alaska. Canadian Journal of Arthropod Identification No. 18
Megachile (Megachiloides) wheeleri Mitchell, 1927
Megachine wheeleri Mitchell, 1927. Psyche 34: 107 (♀).
Megachile spokanensis Mitchell, 1927. Psyche 34: 109 (♂).
Diagnosis. The female of M. wheeleri can be recognized by the combination of 4-dentate mandibles with the emargination between inner and 3rd teeth distinctly oblique, the greatest depth much closer to inner tooth, T5 with punctures separated by 3-4 pd in apical half, the interspaces polished and shiny. They are most similar to M. manifesta. Females of M. manifesta have T5 with rather close punctures (separated by ≤ 1 pd) and dull interspaces. The male of M. wheeleri is distinct, and is recognized by the combination of conspicuously pale coloured and greatly modified front legs, a rounded postmedian tranverse carina on T6, T5 with a white apical fascia, quadrate, smooth and shiny hind tarsomeres, and the mesepisternum with a prominent, flattened, triangular carina-like protuberance just behind the front coxa.
Female: Length 12-13 mm.
Head. 1) compound eyes subparallel; lateral ocelli slightly nearer edge of vertex than to eyes (4:5), 2) clypeal margin straight, shining and impunctate, slightly impressed just above edge, 3) mandible 4-dentate, with an complete cutting edge between 3rd and 4th teeth, incomplete between 2nd and 3rd teeth, emargination between the inner and 3rd teeth distinctly oblique with the greatest depth in the emargination much closer to the inner tooth than to the 3rd tooth (Plate 1, Figure M25), 4) gena slightly wider than compound eye (9:7), 5) punctures quite close and fine on face, and on clypeus above apical impressed area, on vertex medially, shallow on gena, slightly more coarse and sparse on vertex laterally with a few irregular punctures adjacent to upper edge of compound eyes, 6) pubescence white, elongate on face and gena though hardly obscuring surface, mostly brown on vertex though becoming pale on hind margin, 7) F1 longer than broad (2:1.3), slightly longer than pedicel, F2 and F3, subequal in length to following flagellomeres, which are just slightly longer than wide, apical flagellomere elongate (3.5:2).
Mesosoma. 1) pubescence white laterally and posteriorly, and on legs, brown in large part on mesoscutum, the scutellum with a few scattered dark hairs in the otherwise white pubescence, 2) punctures close and fine on most of mesosoma, more coarse and distinctly separated in centre of mesoscutum, shallow but distinct on pleura and propodeum, triangle shiny and impunctate, 3) hind basitarsus slightly narrower and distinctly shorter than its tibia, spurs yellow, 4) tegula reddish-brown, shiny and finely punctate, 5) wings subhyaline, slightly clouded apically, the veins black.
Metasoma. 1) T2 and T3 depressed basally with a subcarinate basal rim, the more apical terga only very slightly depressed basally, terga somewhat more deeply depressed apically, T6 slightly concave at sides in dorsal aspect, rounded apically, straight in profile; punctures very minute and close on basal terga, becoming quite sparse, but still minute to T5, which is polished, punctures fine and close on T6; pubescence white on T1 and T2, discal pubescence black on T3-T5, longer on the more apical terga, T6 with abundant erect black hairs visible in profile, with silvery tomentum apically, T2-T5 with entire white apical fasciae, narrow on the more basal terga, but broad, dense and conspicuous on the more apical ones, 2) scopa white, black on S6 and apically on S5 (occasionally entirely so); punctures coarse and close on sterna, apical margins wide and impunctate.
Male: Length 10-11 mm.
Head. 1) compound eyes slightly converging below; lateral ocelli subequally distant from eyes and edge of vertex, 2) clypeal margin straight and impunctate, 3) mandible 3-dentate, the lower process very robust, subbasal in position, 4) gena subequal to compound eye in width, lower margin of lower concavity produced into a carina-like projection with a apical tuft of hair, 5)punctures fine and shallow on gena, becoming deeper on vertex laterally with distinct shiny interspaces, closer on vertex medially and over entire head, fine and close on clypeus under the dense pubescence, 6) pubescence entirely yellowish-white, with no dark admixture, long and very dense on face below ocelli, sparser on gena below and on vertex, sparse on gena, 7) F1 slightly longer than broad (2:1.5), slightly longer than pedicel, subequal to F2 and the remaining flagellomeres, which are very slightly longer than broad, apical flagellomere flattened and dilated, flagellomeres reddish beneath.
Mesosoma. 1) pubescence entirely yellowish-white, with no dark admixture, tarsal fringes white, the front ones tipped with brown, and yellowish-brown beneath, 2) punctures fine and close over entire dorsal surface of mesosoma, slightly separated on scutellum medially and on pleura above, propodeum with punctures more shallow but still close, triangle somewhat shiny and impunctate, 3) front coxal spine very broad and flat, spatulate, slightly bowed anteriorly, the surface of the coxa polished, with neither setae nor pubescence; front femur widely dilated, the lower margin distinctly bisinuate basally, anterior face polished yellowish-red, posterior face of front tibia polished yellowish-red, otherwise dark; front tarsus dilated, pale yellow, margined posteriorly beneath with brown, the basitarsus basally narrower than its tibia, but expanded apically, the anterior margin deeply excavated, the resulting scale protruding almost to tip of tarsomere 2; mid and hind legs dark, the apical tarsomeres more or less reddish-brown, middle tarsomeres of hind leg quadrate, the apical one considerably thickened, the basitarsus short, subequal to the second and third tarsomeres combined, outer surface shiny, impunctate and lacking pubescence; mesosternum with a flattened, carina-like spine just posterior to each front coxa, spurs yellow, 4) tegula dark reddish-brown, closely punctate throughout, 5) wings subhyaline, slightly clouded apically, the veins black.
Metasoma. 1) T2-T5 only slightly depressed basally, but quite strongly so apically with a distinct subcarinate rim basal to fasciae; carina of T6 entire and down-turned, with coarse and irregular denticulations, apical margin with carinate median teeth that are much nearer the obscure lateral angles than to each other, T7 robust, produced medially into a short triangular projection; punctures minute and close on metasoma basally, becoming slightly more coarse, sparse, and irregular apically on discs to T5, the more apical terga shining, T5 with a well define depression extending medially across disc apical to the basal carinate rim, T6 more coarsely punctate with a basal depression with carinate rim; pubescence entirely yellowish-white on all terga, T2-T5 with entire whitish apical fasciae, 2) S1-S4 exposed, S1 with robust, raised, medially produced projection with a subcarinate median ridge that runs to basal margin of disc, S4 slightly emarginate medially; apical margins of S2-S4 slightly depressed with narrow hyaline margins; punctures on discs close and fine on basal sterna, more separated apically; apical edges with sparse white pubescence that is more elongate laterally, discs very sparsely pale pubescent, hairs scarcely visible.
Genitalia. Plate 2
Discussion. Hobbs and Lilly (1954) suggest his species is the most common Megachile in the mixed prairie region, and the most common member of the subgenus Megachiloides in western Canada. It is often found associated with gum weed (Grindelia squarrosa) (Hobbs and Lilly 1954). This species nests in the ground, though interestingly, Gordon (2000) found that M. wheeleri used trap-nests which were at placed at ground level and those which were buried and positioned at an angle similar to natural (i.e., excavated) nesting tunnels, but not in trap-nests at 1m above the ground.
Distribution. Southern SK and AB.