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 (Litomegachile) gentilis Cresson, 1872
Megachle gentilis Cresson, 1872. Trans. Amer. Entomol. Soc. 4: 267 (♂).
Megachile palmarum Perkins, 1899. Fauna Hawaii. 1: 114 (♂, ♀).
Megachile murinella Cockerell, 1908a. Ann. Mag. Nat. Hist. (8) 1: 263 (♀).
Diagnosis. The female of M. gentilis can be recognized by the combination of 4-dentate mandibles, with the emargination between inner and 3rd teeth with an angulation (appearing as a weakly developed 5th tooth), T6 being weakly concave in lateral view, and S6 with scopal hairs entirely black, S1-S5 with scopal hairs white. They are most similar to M. mendica. The female of M. mendica has T6 straight in lateral view, S6 with only a few black hairs, and S1-S5 with scopal hairs yellow. The male of M. gentilis can be recognized by the combination of simple and dark front tarsi, front coxa possessing a small spine, 3-dentate mandibles, T5 lacking a white apical fascia, and T4 and T5 with punctures close with interspaces indistinct. They are most similar to M. mendica. The male of M. mendica has T4 and T5 with punctures separated with distinct, polished interspaces that are separated by 2-4 pd.
FEMALE: Length 11-12 mm.
Head. 1) compound eyes convergent below; lateral ocelli slightly closer to margin of vertex than eyes (4:5), 2) clypeal margin straight and entire, 3) mandibles 4-dentate, incomplete cutting edge between 2nd and 3rd teeth, complete between 3rd and 4th teeth, but emargination between 3rd and 4th teeth angulate medially, thus approaching a weakly developed 5th tooth (Plate 1, Figure M9), 4) gena narrower than compound eye (4:5), 5) punctures deep and distinct, rather fine, quite close but not crowded across vertex, becoming more fine, shallow and close on gena, more punctatorugose on frons, clypeus shining, punctures well separated medially, becoming quite close on each side, supraclypeal area shining medially, with a distinct impunctate area in lower half, 6) pubescence whitish, quite copious and rather elongate around antennae and paraocular area, more elongate, but sparse on gena below, becoming shorter and rather sparser above, clypeus very sparsely pubescent, pubescence of vertex and adjacent to ocelli black, 7) F1 subequal in length to pedicel and F2, remaining segments slightly longer than broad (2.5:2), apical segment more elongate (3.5:2).
Mesosoma. 1) pubescence short and sparse dorsally, not concealing surface, more dense and elongate, and entirely pale laterally and posteriorly, copius around pronotal lobe and at base of wing, mesoscutum largely with short, erect, black pubescence, scutellum with intermixture of pale and black pubescence, scutello-mesothoracic suture with some very fine, obscure, pale tomentum, 2) mesoscutum and scutellum rather dull, punctures in general fine, crowded, and contiguous, slightly separated in centre of scutellum, quite densely crowded on axilla, somewhat coarser on pleura below, propodeum somewhat smoother with finer punctures and larger interspaces (1-2 pd), triangle dull and impunctate, 3) mid and hind basitarsi slightly narrower than their tibiae, spurs yellow, 4) tegula brownish-black, minutely and rather sparsely punctate, 5) wings sub-hyaline, veins brownish-black.
Metasoma. 1) T2-T5 shallowly grooved across base, basal margin of the groove slightly carinate and complete, apical margins narrowly depressed laterally, but only slightly medially, narrowly white fasciate, discal pubescence short, erect, rather dense, entirely black on T3-T5, with a few black hairs apically on T2 in some specimens, T1 with rather thin but long and erect, entirely pale pubescence, without a distinct apical fascia; terga shining, T2-T5 with punctures fine and well separated medially, with shiny interspaces 1-2 pd apically on disc, becoming somewhat closer laterally; T6 slightly concave in lateral view, with erect, black hairs basally, with some sparse, elongate, erect hairs visible laterally on T5 and T6 in dorsal view, surface very densely and finely punctate and more or less covered with fuscous, appressed tomentum, 2) S6 covered with black scopal hairs, S5 with some black scopal hairs at sides apically in some specimens, scopa otherwise white; S1 and S2 quite closely, uniformly punctate, S3-S5 more coarsely and sparsely so, apical margins very narrowly yellowish-hyaline.
MALE: Length 9-11 mm.
Head. 1) compound eyes convergent below; distance from lateral ocelli to margin of vertex subequal to distance to eyes, 2) clypeal margin nearly straight, but median third very slightly produced, shining and impunctate, very slightly incurved, 3) mandible 3-dentate, lower process triangular, basal in position, 4) gena slightly narrower than compound eye (4:5), 5) punctures deep and distinct, rather fine, slightly separated on vertex laterally, with shiny interspaces, becoming somewhat finer and more shallow and vague on gena, densely crowded below ocelli, entire face around and below antennae densely and finely punctate, almost rugose beneath dense pubescence which completely hides surface, clypeus densely and finely punctate throughout, with narrow but distinctly shining interspaces beneath dense pubescence, 6) pubescence of face yellowish-white, quite copious and elongate below level of median ocellus, that on gena white and more sparse, very elongate below, becoming shorter above, somewhat more yellowish and elongate on vertex, with a few, intermixed dark hairs on vertex, 7) F1 about as long as broad and subequal in length to pedicel, half as long as F2 and remaining flellomeres, which are longer than broad (5:3), apical flagellomere more elongate (4:1.5).
Mesosoma. 1) pubescence greyish-white, more elongate laterally and posteriorly, especially around pronotal lobe and wing base, shorter and very sparse on mesoscutum, whitish and much more elongate on ventral surface and legs, 2) mesoscutum dull, punctures rather fine and densely crowded except in apical half in centre where they are slightly separated, those on axilla and scutellum densely crowded; pleura dull, subrugose, punctures closely crowded; propodeum somewhat shiny, much smoother, with sparce, shallow and obscure punctures, triangle rather dull and impunctate, 3) front coxal spine short, but well developed, triangular, partially concealed by dense, long pubescence; mid tibial spurs rather short but well developed; all basitarsi much narrower than their respective tibiae, spurs yellow, 4) tegula reddish-brown, shining, very minutely and sparsely punctate, 5) wings subhyaline, veins brownish-black.
Metasoma. 1) T2-T5 rather deeply grooved toward base, with a distinct carina, T4 and T5 with narrow pale tomentum arising from beneath basal carina, apical margins very narrowly depressed, especially laterally, very narrowly yellowish-hyaline; T1 and T2 with punctures fine and close, contiguous, somewhat coarser and well separated medially on T3 and T4, becoming slightly closer laterally, T5 with punctures close, large and elongate; apical margin of T4 depressed across entire width; T5 with apical margin very deeply and narrowly depressed, T2-T4 with complete, pale apical fasciae, narrowed medially on T2 and T3, T5 not fasciate; T6 with dense, pale tomentum medially, carina with a deep, evenly rounded emargination, margin on each side very minutely crenulate, median teeth of apical margin slightly nearer each other than to lateral teeth; T7 broadly triangular2) S1-S4 exposed, apical margins of S2-S4 depressed with hyaline margins; S4 slightly, but widely produced medially, S2 and S3 with punctures fine and close with shiny interspaces <1 pd, S4 with punctures very sparse, the disc shining; S1 well covered with white elongate pubescence, discal pubescence of S2-S4 very thin, scarcely visible, S2-S3 with dense white apical fasciae, S4 with fascia laterally.
Genitalia. Plate 2, Figure G9.
Discussion. This species, common in the northwestern United States was first recorded in Canada by Scudder (1996) from one specimen, but has subsequently been collected in ongoing surveys in southern British Columbia (L.R. Best; unpublished data). Megachile gentilis accepts trap-nests (Kim 1992) (Table 1); its occurence in the Hawaiian Islands as an adventives species (Snelling 2003) suggests that it nests in mobile materials such as twigs and/or wood, as suggested for other adventive Megachile (Cane 2003; Sheffield et al. 2010).
Distribution. This species is known from southern BC (see Map 9).