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) perihirta Cockerell, 1898
Megachile perihirta Cockerell, 1898. Ann. Mag. Nat. Hist. (7) 1: 126 (♂).
Megachile latimanus grindeliarum Cockerell, 1904. Entomol. News 15: 33 (♀).
Diagnosis. The female of M. perihirta can be recognized by the combination of 5-dentate mandibles, with the 4th tooth approximately parallel-sided throughout its length, with an oblique emargination between 3rd and 4th teeth which is much deeper than emargination between 2nd and 3rd teeth, the metasomal terga with fasciae less dense and usually interrupted medially on the more basal terga, the black pubescence of mesoscutum usually occupying the posterior half and extending to scutellum, T2 with discal pubescence usually black in apical half, T6 with intermixture of black and pale pubescence, and a distinct median impunctate area on the clypeus. They are most similar to M. dentitarsus and M. latimanus. Females of M. dentitarsus have relatively dense and conspicuous white metasomal fasciae, and the absence of dark pubescence on the mesosoma. Females of M. latimanus have the the black pubescence of mesoscutum scarcely occupying half of surface and usually not extending to the scutellum, T2 with discal pubescence entirely pale or almost so, T6 with mostly pale pubescence, and by the absence of a distinct median impunctate area on the clypeus. The male of M. perihirta can be recognized by the mid-tibial spur being absent, the ventral protuberance of the mid basitarsus being keel-shaped, and the low carinae on the mesosternum. They are most similar to M. dentitarsus and M. latimanus. The male of M. dentitarsus has small sharp spines on the mesosternum. Males of both M. dentitarsus and M. latimanus have the mid basitarsus bearing a large, quadrate ventral protuberance.
FEMALE: Length 13-14 mm.
Head. 1) compound eyes parallel; lateral ocelli slightly nearer margin of vertex than eyes (3.5:4), 2) clypeal margin straight, minutely and rather sparsely denticulate, 3) mandibles 5-dentate, with the 4th tooth approximately parallel-sided throughout its mid-length; deep oblique emargination between the 3rd and 4th teeth much deeper than emargination between the 2nd and 3rd teeth, width of emargination between 3rd and 4th teeth subequal or at most two times width of the 4th tooth at midlength, with complete cutting edges between 3rd and 4th and 4th and 5th teeth, incomplete between 2nd and 3rd teeth (Plate 1, Figure M38), 4) gena slightly broader than compound eye (5:4), 5) punctures of vertex deep and distinct, rather fine, close medially, becoming slightly separated laterally, minute, close and obscure on gena; frons densely rugosopunctate, somewhat smoother or very minutely rugose laterally beneath the pubescence, supraclypeal area shining, especially medially, with scattered, rather deep and distinct punctures laterally, clypeus with a rather distinct, median impunctate band, punctures otherwise rather deep, distinct and fine, and closely crowded throughout, 6) pubescence around and on face below pale yellowish, quite copious but not very long, somewhat longer and sparser, and entirely yellowish on gena below, becoming shorter above, vertex with considerable, somewhat shorter but erect and conspicuous black pubescence that extends down inner eye margin about ¼ of its length, 7) F1 slightly longer than broad (2: 1.5), longer than pedicel and F2, which is quadrate, subequal in length to remaining flagellomeres, which are slightly longer than broad (2.3:2), apical flagellomere more elongate (3.5:2).
Mesosoma. 1) pubescence mostly pale, quite dense and copious laterally and posteriorly, mesoscutum with considerable, somewhat shorter but erect and conspicuous black pubescence, scutellum with long black hairs intermixed with pale hairs, 2) mesoscutum and scutellum very finely, closely and quite deeply punctate throughout; pleura very finely and densely punctate, propodeum somewhat more shining and smooth with minute, rather close, vague punctures that are slightly separated medially, triangle dull and impunctate, 3) mid and hind basitarsi nearly as broad as their tibiae, hind basitarsus nearly equal to its tibia in length, spurs pale yellow, 4) tegula rather dull, minutely and very closely punctate, 5) wings subhyaline, faintly clouded apically, veins brownish.
Metasoma. 1) T2-T4 shallowly depressed across base, basal margin of depressions distinct but hardly carinate, apical margins of terga rather narrowly depressed, yellowish fasciate at least laterally; discal pubescence of T1 and T2 long, erect and quite copious, entirely pale yellowish on T1, black apically on T2, black over most of T3-T5; punctures of terga minute but rather close, becoming very close at sides; T6 very slightly concave in profile, pubescence entirely dark, with a few suberect black hairs, punctures fine and densely crowded throughout, 2) S6 covered with yellowish scopal hairs, but these becoming somewhat sparse apically, with a dense fringe of short hairs apically; scopa otherwise orange in color; the more basal sterna very finely and densely punctate, punctures becoming slightly more widely separated and coarse on the more apical sterna, apical margins very narrowly yellowish-hyaline.
MALE: Length 12-13 mm.
Head. 1) compound eyes subparallel to slightly convergent below; lateral ocelli subequally distant from eyes and margin of vertex, 2) clypeal margin very slightly incurved on each side, medially with a few tubercles or crenulations, 3) mandibles 3-dentate, outer margin curved as seen from above, lower edge amber in colour, lower process quite narrow and elongate, apex obliquely acute, densely pubescent on inner surface, basal in position, 4) gena wider than compound eye (3:2), with a concave, shelf-like tubercle at lower margin that receives tip of the lower mandibular process when closed, 5) vertex very finely and closely punctate medially, punctures becoming somewhat more coarse and distinctly separated laterally, very fine and dense on gena; frons finely and densely rugosopunctate, supraclypeal area finely and densely punctate, with a prominent medial tubercle just below level of antennae, clypeus very finely and densely punctate with a rather wide impunctate area along apical rim, 6) pubescence pale yellowish, copious and elongate around antennae and lower half of face, sparser and erect on vertex, short and sparse on gena, which have a pair of lines of short white hairs along lower margin, 7) F1 slightly longer than pedicel, and 2/3 as long as F2; remaining flagellomeres slightly longer than F2, apical flagellomere elongate and slightly dilated, rather strongly flattened.
Mesosoma. 1) pubescence entirely pale, more whitish on pleura below, yellow on propodeum and on pleura above, on mesoscutum and scutellum dense, elongate and bright yellow, 2) mesoscutum dull, punctures very fine and densely crowded throughout, those on scutellum very minute, close but relatively distinct, pleura somewhat shining beneath pubescence, punctures very fine, shallow and close throughout, propodeum shining laterally, rather dull, with minute, indistinct, fine punctures separated by >1 pd, triangle dull and impunctate, 3) front coxal spine robust, rather slender, subacute apically, anterior face of coxa entirely bare, without patch of setae; front tarsus yellow, basitarsus quite broadly dilated at base, very slightly narrowed apically, quite deeply excavated anteriorly, tarsal fringe pale yellow, very dense and elongate; front tibia largely reddish-brown, becoming yellow at tip, occasionally with black spot medially; posterior face of front femur black apically, but otherwise largely brownish, densely fringed posteriorly, outer hairs pale yellowish, inner hairs more orange; mesosternum with a low carina just anterior to mid coxa; mid and hind femora swollen, mid basitarsus with a keel shaped process covering most of lower surface; hind basitarsus medially expanded, about half as broad as long, anterior margin evenly curved, 4) tegula brownish, minutely and very closely punctate, 5) wings subhyaline basally, becoming faintly clouded apically, veins brownish.
Metasoma. 1) T2-T5 rather shallowly depressed across base, basal margin of groove distinct but hardly carinate, apical margins of basal terga rather abruptly depressed laterally, fully depressed on the more apical terga, margins yellowish-hyaline, fringed with pale hairs that form rather loose, indefinite fasciae; discal pubescence of all terga rather long, erect, entirely pale yellow; punctures of terga minute and quite close, becoming somewhat more distinct on the more apical terga, T6 finely and densely punctate, carina definite but rather low, irregularly serrate across median area, emargination very shallow or absent, median teeth of apical margin prominent and acute, considerably nearer the small, barely visible, lateral teeth than each other; T7 prominent, transverse, rather broadly triangular, apex obtusely angulate, 2) S1-S4 exposed, finely and closely punctate, apical margins rather deeply depressed, yellowish hyaline, more or less fringed with rather elongate, pale yellowish hairs, discs of sterna sparsely pubescent, not at all hiding the surface.
Genitalia: Plate 2.
Discussion. This species and M. latimanus can be regarded as an eastern (M. latimanus) and a western (M. perihirta) sibling species pair, although their ranges overlap in central Canada (ON-AB). Although distinct morpholical differences distinguish the males, only subtle characters separate the females. Megachile perihirta, like M. latimanus, is a ground-nesting species.
Distribution. Found primarily in western Canada from SK-BC and into the western subarctic, though occasionally found as far east as ON.