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) casadae Cockerell, 1898
Megachile casadae Cockerell, 1898. Ann. Mag. Nat. Hist. (7) 1: 127 (♂).
Megachile populi Cockerell, 1900. Ann. Mag. Nat. Hist. (7) 6: 17 (♀).
Megachile opuntiarum Cockerell, 1906a. Ann. Mag. Nat. Hist. (7) 17: 229 (♀).
Megachile austinensis Mitchell, 1927. Psyche 34: 105 (♀).
Diagnosis. The female of M. casadae is distinct and 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, and the clypeal surface which is shiny and sparsely punctate. The male of M. casadae is also 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, and the clypeal surface which is shiny and sparsely punctate. Other members of the subgenus Megachiloides in Canada have a densely punctate clypeus in both sexes.
Female: Length 12-14 mm.
Head. 1) compound eyes subparallel; lateral ocelli slightly closer to edge of vertex than to eyes (5:6), 2) clypeal margin straight, shining and broadly impunctate, slightly impressed just above the edge, 3) mandible 4-dentate, with an incomplete cutting edge between 2nd and 3rd teeth, complete between 3rd and inner teeth, emargination between inner and 3rd teeth distinctly oblique with greatest depth in emargination much closer to the inner tooth than to 3rd tooth (Plate 1, Figure M20), 4) gena subequal to compound eye in width, 5) punctures very fine and close on most of face, clypeus and supraclypeal area shiny and sparsely punctate, especially medially, punctures becoming more coarse and distinct laterally, punctures fine and close on vertex, becoming more sparse (1pd) along upper inner eye margin, shallow on gena, 6) pubescence short and dense on face around antennae, white to pale yellow on face and gena, yellowish-brown on vertex, 7) F1 slightly longer than broad (4:3), longer than pedicel and F2, which is quadrate, subequal in length to remaining flagellomeres, apical flagellomere more elongate (2:1).
Mesosoma. 1) pubescence dense and rather short, white on pleura, propodeum, mesoscutum anteriorly, scutellum, and legs, brownish, short and erect on most of mesoscutum, 2) punctures very close and fine laterally on mesoscutum and scutellum, with shiny interspaces of 1 pd (or slightly more) medially; punctures of pleura and propodeum fine and close (< 1 pd), triangle somewhat shiny and impunctate, 3) mid and hind basitarsi distinctly shorter than their tibiae, hind basitarus about as wide as tibia, spurs yellow, 4) tegula black, finely punctate throughout, anterior margin pubescent, 5) wings subhyaline, slightly clouded apically, the veins black.
Metasoma. 1) T2-T5 depressed basally with a distinct, complete carinate rim, terga somewhat more deeply depressed apically; T6 in dorsal aspect only slightly concave at sides, rounded apically, straight to very slightly concave in profile; punctures minute and very close on T1, becoming more distinct but still quite close on T2 and T3, becoming more sparse (≥ 1 pd) on T4 and T5, fine and crowded on T6; pubescence white on T1, T2-T5 with erect blackish pubescence, T6 with some black pubsence basally, with silvery tomentum apically, T2-T5 with entire white apical fasciae, these narrower on the more basal terga, broad, dense and conspicuous on the more apical ones, 2) scopa black on S6 except at base, otherwise yellowish-white, punctures coarse and close, becoming slightly more separated on more apical sterna.
Male: Length 12-14 mm.
Head. 1) compound eyes subparallel to slightly convergent below; lateral ocelli subequally distant from eyes and edge of vertex, 2) clypeal margin straight, 3) mandible 3-dentate, with 2nd tooth much closer to apical tooth than inner tooth, the lower process very robust, subbasal in position, 4) gena slightly wider than compound eye (7:5), lower margin of lower concavity produced into a carina-like projection with a apical tuft of yellowish-brown hair, 5) punctures fine and close on head, slightly separated (1 pd) on vertex near ocelli and adjacent to upper eye margin, becoming shallow on gena, clypeus with fine, sparse punctures, interspaces shining (1-2 pd), apical margin narrowly impunctate, 6) pubescence pale yellowish-brown and sparse on vertex, becoming white below with no dark admixture, very long and dense on clypeus, pointing downward, that on supraclyeal area and around antennae shorter and pointing upward, more sparse on gena, 7) F1 quadrate, subequal in length to pedicel, shorter than F2 and remaining flagellomeres which are longer than broad (3:2), apical flagellomere flattened and somewhat dilated.
Mesosoma. 1) pubescence long, pale yellow on mesoscutum, becoming long and dense below, fading to white with no dark admixture, tarsal fringes long, white, the front tarsal fringe with brownish-black hairs ventrally, 2) punctures fine and close throughout, slightly separated (1 pd) medially on mesoscutum and scutellum and propodeum, triangle rather dull and impunctate, 3) front coxal spine narrow, about twice as long as broad, slightly bowed anteriorly, coxal surface polished, with a small patch of reddish setae at base of spine; front femur widely dilated, the lower margin distinctly bisinuate basally, anterior and posterior faces of front femur and tibia with polished yellowish-red areas, otherwise dark, front tarsus pale yellow, the posterior margin beneath with black areas; front tarsus slightly dilated, basitarsal margins subparallel, subequal to tibia in width, the anterior margin; mesosternum neither carinate nor spined anteriorly; hind baistarsus subequal in length to tarsomeres 2-4 combined, much longer than wide, and much shorter than tibia, spurs yellow, 4) tegula yellowish-brown, finely punctate, 5) wings subhyaline, the veins yellowish-brown.
Metasoma. 1) T2-T6 depressed basally with strong carinate rim, strongly depressed apically; carina of T6 broadly trianglular with fine irregular denticulations, apical margin with carinate median teeth much nearer less prominent lateral teeth than each other; T7 robust, produced medially into a spine-like projection which is longer than basal width; punctures minute and close on basal terga, becoming slightly more coarse and sparse to T5, the more apical terga shining with interspaces 1 pd, T6 more coarsely punctate; discal pubescence sparse and entirely pale on T1 and T2, dense and elongate on T1; T3-T5 with mostly black erect hairs in apical half, entire whitish apical fasciae on T2-T5, with long white, dense hairs below carina of T6, 2) S1-S4 visible, punctures fine with shiny interspaces, apical margins depressed and hyaline, disc with very short, fine pale pubescent, scarcely visible, more elongate laterally, with long white apical fasciae on lateral margins of S2-S4.
Genitalia. Plate 2, Figure G20.
Discussion. This is the first record of this species in Canada. Two female specimens were collected in pan traps at Onefour, Alberta (N49 09.37, W110 16.397, 900m), one on 20.vii.2010, the second on 29.vii.2010; N. de Silva collector. Like other Megachiloides, this species is probably a ground nester (Table 1).
Distribution: Southern AB.