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 (Xanthosarus) circumcincta (Kirby, 1802)
Apis circumcincta Kirby, 1802. Monogr. Apum Angl., 2: 235 (♀).
Megachile giliae Cockerell, 1906b. Bull. Amer. Mus. Nat. Hist. 22: 452 (♂). New Synonymy.
Megachile circumcincta var lactescens Cockerell, 1928. Ann. Mag. Nat. Hist. (10) 1: 355 (♀).
Megachile circumcincta var. griseohirta Alfken, 1929 Ark. Zool. 20A: 7 (♀).
Megachile circumcincta var insidiosa Benoist, 1940. Ann. Soc. Entomol. France 109: 49 (♂,♀).
Megachile (Macromegachile) circumcincta ozbeki Tkalců, 1977. VÍst. cs. Spolec. zool. 41: 235 (♂,♀).
Megachile (Delomegachile) circumcincta numidica Tkalců, 1988. VÍst. cs. Spolec. zool. 52: 57 (♀).
Megachile (Macromegachile) circumcincta etnaensis van der Zanden, 1989. Entomol. Abh. Mus. Tierkd. Dresden 53(6): 73 (sex).
Megachile (Xanthosaurus) circumcincta chinensis Wu, 2006. Fauna Sinica, Insecta 44: 302 (♂,♀) (preoccupied; not Megachile chinensis Radoszkowski, 1874).
Diagnosis. The female of M. circumcincta can be recognized by the combination of the metasoma, which lacks pale apical fasciae on the terga, giving a distinctive pattern of all pale hairs (T1 and T2) and black hairs (T3-T6) in dorsal view, the mandible tapering gradually but continuously from base to apex in lateral view, with the inner mandibular tooth rounded and narrower, and the pale pubescence on the ventral surface of the mesosoma. They are most similar to M. gemula and M. melanophaea. Females of M. gemula have the upper and lower margins of the mandible parallel in lateral view from the base to a length subequal to width prior to tapering, and the broadly truncate inner mandibular tooth. Females of M. melanophaea have the inner mandibular tooth with a small excision at its apex, and dark pubescence ventrally on the mesosoma. The male of M. circumcincta can be recognized by the combination of 4-dentate mandibles, the front basitarsus largely pale in colour, dilated and excavated along the anterior margin, the apical rim of front tibia with a short and strongly tapered spine, and T5 with a pale apical fascia. They are most similar to M. gemula and M. melanophaea. Males of M. gemula have the front basitarsus dilated and excavated along the anterior margin, but with the colour mostly black (i.e., not conspicuously pale coloured), and lack a pale apical fasciae on T5. Males of M. melanophaea have the apical rim of front tibia with a strongly flattened and rounded tubercle projecting posteriorly.
FEMALE: Length 10-13 mm.
Head. 1) compound eyes subparallel; lateral ocelli nearer margin of vertex than to eye (4:5.5), 2) clypeal margin straight, but very finely crenulate with a small central crenulation, apical rim impunctate and shiny, 3) mandibles 4-dentate, with a complete cutting edge between the 3rd and inner teeth, inner tooth rounded and narrow (Plate 1, Figure M31), mandible with upper and lower margins in lateral view tapering gradually and evenly from base, 4) gena broader than compound eye (9:7), 5) punctures of vertex quite deep and distinct, rather fine, close medially, becoming well separated laterally, fine and close on gena above, more crowded and minute below; frons dull and densely rugose, supraclypeal area shining, punctures fine and slightly separated, clypeus with a raised impunctate line extending from top to bottom margin, ending at a central crenulation, punctures otherwise close and fine, 6) pubescence elongate and yellowish-white around antennae and lower part of face, clypeus with hairs entirely brown medially with a few pale hairs on lateral margins, vertex with erect, elongate, pale hairs intermixed with shorter, brown hairs, pubescence becoming largely brownish on gena and on inner margin of compound eyes, 7) F1 narrow, and longer than broad (2:1), longer than pedicel and remaining flagellomeres, F2 and F3 quadrate, remaining flagellomeres slightly longer than broad (2:1.5).
Mesosoma. 1) pubescence copious, elongate, yellowish-white laterally and posteriorly, and entirely pale on underside of mesosoma and on legs; mesoscutum with long, erect pubescence that is pale anteriorly, with brownish hairs intermixed across posterior half, pubescence long, erect and mostly pale on scutellum, 2) mesoscutum shining, punctures quite deep and distinct, moderately coarse, sparser in centre of disc, becoming close laterally; scutellum with fine and rather sparse punctures on mid-line but becoming rather closely punctate on each side, punctures of axilla very fine and crowded; pleura dull, punctures fine and very close, becoming minute and crowded above; propodeum smooth but dull, with only exceedingly vague, shallow and minute punctures, triangle dull and impunctate, 3) mid and hind basitarsi about as broad as their tibiae, but somewhat shorter, spurs yellowish, 4) tegula smooth, with only exceedingly minute punctures anteriorly, 5) wings subhyaline, veins brownish-black.
Metasoma. 1) T2 and T3 shallowly depressed across base, scarcely grooved, basal margin evident but not sharply carinate, apical margins of T2-T4 very shallowly but rather broadly depressed, entirely lacking fasciae; discal pubescence of T1,T2 and basally of T3 long, erect, and entirely pale, quite long, erect and entirely black on most of T3, T4-T6, T6 nearly straight in profile, with golden subappressed pubescence; median punctures of basal terga exceedingly minute and quite sparse, becoming closer laterally, sparser and larger on T3-T6; T6 densely and finely punctate throughout, 2) S6 covered with scopal hairs, these becoming somewhat sparse toward apex, which is fringed with short hairs; scopa largely reddish, often tinged with brown toward base; the more basal sterna closely and rather finely punctate, somewhat more widely separated apically on the apical sterna.
Male: Length 10-11 mm.
Head. 1) compound eyes very slightly convergent below; lateral ocelli subequally distant from eyes and edge of vertex, 2) clypeal margin straight, but with a few minute median crenulations, 3) mandible 4-dentate, outer margin regularly curved in dorsal view, without a median angle, lower process acute, subbasal in position, 4) gena slightly broader than compound eye (7:5), lower margin of lower concavity produced into a low carina-like projection, 5) punctures fine and close on gena, on vertex medially, on face below median ocellus and on clypeus, somewhat more coarse and sparse on vertex laterally and between lateral ocelli and eyes, 6) pubescence white or pale yellow on head, copious on face below ocelli, with a few inconspicuous dark hairs on vertex laterally and behind eyes, short and sparse on gena, which have a pair of lines of short white hairs along lower margin, 7) F1 slightly longer than broad (5:4), longer than pedicel and F2, and about as long as remaining flagellomeres, apical flagellomere flattened and somewhat dilated.
Mesosoma. 1) pubescence white or pale yellow on mesosoma and legs, front tibia with a few short dark hairs anteriorly and with elongate dark hairs basally on front femur, front tarsal fringe white, yellowish beneath, mid and hind basitarsi with rather distinct fringes of long white hairs, 2) punctures fine and close on mesoscutum, slightly separated medially in anterior half, fine and close on scutellum and pleura, propodeum with fine but close punctures, triangle smooth and dull, 3) front coxal spine flattened, apically rounded, fully twice as long as broad, coxa bare anteriorly, with a rather large dense patch of short reddish-brown bristles in front of spine; front femur apically slightly keeled beneath, black on posterior face, yellowish to reddish on upper face, the anterior face more yellowish, often with a thin dark stripe along lower margin, at least toward the base; front basitarsus dilated and flattened, black on outer face except for yellow apex, yellowish to reddish on the other two faces; front tarsomeres yellow, a dark spot ventrally on tarsomere 2, the basitarsus subequal to tarsomeres 2-4 in length, very slightly broader apically than at base, the anterior margin with a rather shallow excavation, the apex only slightly produced; mid and hind basitarsi about twice as long as broad, spurs yellowish, 4) tegula reddish-brown, closely and finely punctate anteriorly, becoming sparser in posterior half, 5) wings subhyaline, the veins brown.
Metasoma. 1) T2-T5 very slightly depressed basally, basal ridge of T4-T5 present but hardly carinate, carina of T6 with small but distinct median emargination, apical margin with distinct median teeth that are slightly closer to obscure lateral teeth than to each other, T7 with acute spine; apical margins of T3-T5 depressed, T4-T5 with more or less obscure white apical fasciae, and T3 with a trace of one toward sides; punctures minute and close on terga, somewhat more sparse toward T5, slightly closer on T6; pubescence white or pale yellowish on T1-T3, T4-T5 with rather long conspicuous dark pubescence on discs, T6 with pubescence sparse and pale below carina, 2) S1-S4 visible; apical margins depressed and narrowly hyaline, S4 more broadly so; sterna finely and closely punctate basally, becoming slightly more spaced on apical sterna; discs of sterna very sparsely pale pubescent, becoming more elongate laterally, apical margins of S1-S3 with thin pale fasciae.
Genitalia. Plate 2, Figure G31.
Discussion: Megachile giliae is synonymised here for the first time with M. circumcincta of the Old World. Mitchell (1935b) made note of the similarity of M. giliae to the Palaearctic species, though hesitated to synonymise the two because the female was unknown. The synonymy made here was facilitated by the discovery of the female and the subsequent CO1 sequence match to the Old World species. Genitalia and other morphological characters were examined and matched among specimens examined from both the New and Old World. This species is a ground nester.
Distribution: Holarctic; western Canada, and into subarctic areas of western NT, YT and Alaska.