Nearctica, Rightmyer, Molly G., Griswold, Terry & Arduser, Michael S., 2010

Rightmyer, Molly G., Griswold, Terry & Arduser, Michael S., 2010, A review of the non-metallic Osmia (Melanosmia) found in North America, with additional notes on palearctic Melanosmia (Hymenoptera, Megachilidae), ZooKeys 60, pp. 37-77 : 55-60

Osmia Melanosmia nearctica Rightmyer, Griswold, & Arduser sp. n. Figs 9, 103351

Diagnosis.

Osmia nearctica is one of two members of the xanthomelana species group in North America; characters to distinguish it from the other member of that group, Osmia maritima , are given under that species (see above).

In the Palearctic, Osmia nearctica is most similar to Osmia xanthomelana , but can be differentiated from that species by the following characters: In females, the propodeal triangle is shining but weakly shagreened throughout (Fig. 36) ( Osmia xanthomelana with entirely polished, strongly shining lower half of the propodeal triangle), the outer hind tibial spur is only about half the length of the hind basitarsal segment ( Osmia xanthomelana with outer hind tibial spur nearly three-fourths length of hind basitarsal segment), and the lower margin of the mandible has a distinct, translucent flange that curves away from the condylar ridge ( Osmia xanthomelana with the lower margin of the mandible opaque, forming a ridge that is parallel to the condylar ridge). The hairs of the mesepisternum tend to be dark brown in Osmia nearctica , while in Osmia xanthomelana the hairs tend to be pale yellow to white, and the hairs of the hypostomal area tend to be denser in Osmia nearctica than in Osmia xanthomelana .

In males, the propodeal triangle is weakly shagreened throughout in Osmia nearctica (Fig. 41) ( Osmia xanthomelana with entirely polished, strongly shining lower half of the propodeal triangle); the lower tooth of the mandible is only slightly longer than the upper tooth in Osmia nearctica (in Osmia xanthomelana the lower tooth of the mandible is much longer than the upper tooth and the entire apical margin of the mandible is conspicuously wider than the middle, approaching the look of male Acanthosmioides ); T7 midapically has a shallower emargination in Osmia nearctica (Fig. 43) than in Osmia xanthomelana ; the S6 midapical truncation is clearly emarginate in Osmia nearctica (Fig. 47) ( Osmia xanthomelana with S6 truncation not emarginate); and the apical tip of the gonoforceps (apical to subapical swelling) is more rounded in Osmia nearctica (Figs 49, 50) (in Osmia xanthomelana the apical tip is more pointed). Osmia nearctica can be differentiated from Osmia maritima and Osmia alticola by the microscopic hairs on the underside of the flagellar segments ( Osmia maritima and Osmia alticola with conspicuous hairs about half the width of the flagellar segments).

Description.

Female. Figs 9, 10, 33-38. Total length: 9.0-11.5 mm; forewing length: 6.5-7.2 mm; length of lateral ocellus to preoccipital margin 0.6 mm; length of lateral ocellus to compound eye 0.7 mm.

Color: Dark brown to brown-black, sometimes with reddish overtones especially on mouthparts, labrum, mandible, flagellar segments, legs, and apical margins of T 1-T5. Wings moderately infuscate, more strongly infuscate in marginal cell and distal to cells.

Pubescence: Clypeus below apical margin with lateral tuft of golden, medioposteriorly directed hairs. Brown, minutely branched hairs on most of body except as follows: white to yellow, minutely branched hairs interspersed with brown on outer surface of mandible, face excluding ventral third of clypeus and sometimes on vertex (and gena), and dorsal surfaces of T2, T5, T6; almost entirely white to yellow, minutely branched hairs on vertex (sometimes), mesoscutum, mesoscutellum, metanotum, dorsally on propodeum (excluding triangle), pronotal lobe, and dorsal surface of T1; brown, simple hairs interspersed with minutely branched hairs on most of body, except simple hairs lacking on dorsal mesosoma; simple hairs only (no branched hairs), golden on all tarsi and brown on scopa; brown, short, simple hairs evenly covering forewing. Galea and basal two labial palpal segments with hairs on lateral margins straight, 0.2-0.5 OD in length. Labrum with long hairs arranged in two curved, transverse rows, along subapical margin and approximately at midpoint, with additional fringe of shorter hairs at apical margin. Clypeus with hairs about as dense as on frons. Hypostomal area with hairs densely distributed across area, straight to weakly incurved at apical tips, 3.0-4.0 OD in length.

Punctation: Head and mesosoma with punctures nearly contiguous, more or less round, and moderately impressed except as follows: labrum mostly impunctate except near fringes of hairs; clypeus with impunctate midapical truncation about length of F2 or little longer (Fig. 35); mesoscutum posterior to median longitudinal sulcus with punctures separated by up to a puncture diameter; mesepisternum with punctures less strongly impressed, nearly contiguous to separated by about half a puncture diameter; hypostomal area near angle and legs with punctures shallowly impressed, sometimes elongated into oval shape; tegula with punctures minute, sparser medially and posteriorly, separated by up to three or four puncture diameters; pronotum, metepisternum, metanotum, and lateral and posterior surfaces of propodeum with punctures very weakly impressed, with background integument weakly shagreened; propodeal triangle with dorsal fourth reticulate, lower three fourths shagreened, weakly shining (Fig. 36). T1 anterior surface weakly shagreened, shining, with scattered punctures at dorsolateral angle; T1-T3 dorsal surfaces very weakly shagreened, shining, excluding apical impunctate margins with small punctures nearly contiguous to separated by 1.0 puncture diameter (on T1, Fig. 37) to separated between 1.0 to 3.0 puncture diameters (on T3); apical impunctate bands 2.0-4.0 puncture diameters in length. T4-T5 dorsal surfaces shagreened, weakly shining, excluding apical impunctate bands with punctures nearly contiguous to separated by 2.0 puncture diameters; apical impunctate bands about 5.0-8.0 puncture diameters in length. T6 with punctures minute, nearly contiguous, mostly obscured beneath dense hairs.

Structure: Labial palpus four-segmented, second labial palpal segment subequal to or ca. one-fourth longer than basal-most segment. Mandible with outer and condylar ridges of subequal thickness, parallel along length (Fig. 9); apical margin with four well-developed teeth, lacking carina separating third tooth from second and fourth, margin of third tooth forming distinct V-shape with adjacent margin of second and slightly smaller V-shape with adjacent margin of fourth, third tooth more or less on same plane as second and fourth (Fig 10); inner, ventral margin of mandible lacking distinct tooth, diverging away from condylar ridge basally; mandible apically widened (ca. 1.7 times wider than median width), first tooth longer than other teeth, length between apical tips of second and fourth teeth subequal to slightly wider than apical tips of first and second teeth (Fig. 10). Clypeus apical margin with distinct truncation on middle half, this truncation with lateral corner slightly produced, forming weak protuberance relative to apical margin of truncation and forming ca. 90 degree angle with apical margin of clypeus lateral to truncation (Fig. 35). F1 twice length of F2, remaining apical flagellar segments gradually increasing in length such that F10 subequal to F1 or little longer. Vertex behind lateral ocellus 2.0-2.5 OD in length. Genal width 1.5 to nearly 2.0 times that of compound eye in lateral view. Preoccipital margin rounded, not carinate. Hypostomal carina moderately high, highest at about midpoint of hypostomal area posterior to angle and forming distinct triangular projection at this point, tapering to low carina or near obsolescence at angle. Malus forming pointed apical spine. Foretarsal and midtarsal segments excluding basitarsal and apical-most segments with anterior lobes slightly longer than posterior; hind tarsal segments not swollen. Hind tibial spurs weakly curved, outer spur about a fifth shorter than inner. Hind basitarsal segment with lateral margins of outer surface parallel.

Male. Figs 39-51. Total length: 8.6 mm (8.0-9.1 mm); forewing length: 6.0 mm (6.0-6.5 mm); length of lateral ocellus to preoccipital margin 0.5; length of lateral ocellus to compound eye 0.6 mm.

Color: Black to dark brown, sometimes with reddish overtones especially on mouthparts, labrum, mandible, flagellar segments, legs, and apical margins of T1-T6 and S1-S3. Wings mostly clear except weakly infuscate along leading edge of forewing, especially along dorsal half of marginal cell.

Pubescence: White to pale golden, minutely branched hairs on body except golden to pale golden, stouter, simple hairs on inner surfaces of tarsi, S4, and S6, and intermixed with white, branched hairs on mandible, lower gena, and outer surfaces of tarsi. Labrum with row of hairs across approximate midline, sparsely covered with hairs on apical fourth and with hairs forming short fringe at apical margin. S2 with hairs at apical third ca. 1.5 to 2.0 OD in length. S3 with medially directed hairs filling entire emargination (hairs ca. 1.0 OD in length medially, 2.0 OD laterally) (Fig. 44). S4 with weakly defined, asetose longitudinal strip, otherwise covered with regularly spaced, simple, short, weakly distally hooked, golden hairs arising from papillate bases (Fig. 44). S6 midapical truncation with very sparse, short, simple hairs arising from papillate bases (Fig. 47).

Punctation: Head with punctures ovate to nearly circular, separated by one-fourth to one-half puncture diameter (up to 1.0 puncture diameter posterior to compound eye) and deeply impressed except as follows: labrum mostly impunctate on basal two-thirds; clypeus with impunctate band along apical margin, about one-fourth length of F1; disc of clypeus, interantennal area, and paraocular area with punctures small, ovate, and nearly contiguous (punctures mostly obscured beneath dense hairs); hypostomal area anteriorly near angle with punctures weakly, shallowly impressed. Mesosoma with punctures more or less round, nearly contiguous to separated by up to a half puncture diameter, deeply impressed except as follows: mesoscutum immediately posterior to median longitudinal sulcus with punctures separated by up to one, sometimes as much as two puncture diameters; tegula with punctures minute, sparse medially, separated by up to five puncture diameters; pronotum, dorsal half of metepisternum and lateral and posterior surface of propodeum weakly shagreened, with moderately impressed, larger punctures; ventral half of metepisternum mostly impunctate, weakly shining; propodeal triangle lineolate to reticulate on dorsal third, shagreened and weakly shining on ventral two-thirds; legs with inner surfaces of femora and tibiae shining, with scattered smaller punctures. T1 with anterior surface very weakly shagreened, shining; T1-T2 with dorsal surfaces excluding apical margins weakly shagreened, shining; T3, T6-T7 dorsal surfaces moderately shagreened; T4-T5 dorsal surfaces strongly shagreened, dull; metasomal terga with apical impunctate margins polished. T1 dorsal surface with punctures minute, distinct and well-impressed, nearly contiguous to separated by a puncture diameter; apical impunctate margin ca. 4.0-5.0 puncture diameters in length (sometimes medially as long as 6.0-7.0 puncture diameters in length). T2-T7 with punctures minute, T2 with punctures separated by ca. 1.0 puncture diameter medially, successively posterior terga with punctures progressively becoming more widely spaced to about 3.0 puncture diameters apart on disc of T6; T2-T6 with apical impunctate margins 4.0-8.0 puncture diameters in length, T7 lacking apical impunctate margin. S1-3 with punctures minute, well-impressed, nearly contiguous to separated by ca. 1.0 puncture diameter. S4-S6 lacking distinct punctures, weakly shagreened.

Structure: Mandible with outer and condylar ridges converging apically; apical margin with two teeth, upper tooth distinctly shorter and wider than lower; inner, ventral margin of mandible very weakly diverging away from condylar ridge basally. Clypeus apical margin mostly linear except with weak irregular tubercles above tufts of setae below apical margin at each side. Flagellar segments subequal in length, except F1 slightly shorter than F2 and F11 slightly longer than F10. Vertex behind lateral ocellus 1.5-2.0 OD in length. Genal width in lateral view ventrally subequal to, dorsally ca. 1.3 times wider than, width of compound eye. Preoccipital margin rounded, not carinate. Hypostomal carina relatively short, gradually tapering to near obsolescence at angle, not forming distinct tooth. Malus forming distinct apical spine. Foretarsal segments excluding basitarsal and apical-most segments with anterior lobes slightly more swollen than posterior. Mid- and hind tarsal segments not swollen. Midfemur with swollen projection on ventral surface. Hind tibial spurs weakly curved at apical sixth, outer spur ca. one-fifth shorter than inner. Hind basitarsal segment widening about a third from apical margin, with strong tooth on inner margin at widest point (Fig. 42). T6 midapically with wide, shallow emargination, forming ca. one-fourth of circle in outline (Fig. 43); T6 lateroapical margin slightly concave sublaterally, forming weak lobe. T7 midapically strongly emarginate, forming semicircle about as wide as, or slightly wider than, deep (ca. 1.5 OD wide; Fig. 43), with spines on either side of emargination rounded, basally nearly as wide as emargination width. S2 strongly convex, covering most of S3. S3 with midapical emargination one-third entire width of sternum and nearly as long as wide (Fig. 44). S4 with apical margin evenly convex, with very weakly defined midapical truncation (Fig. 44). S5 with apical margin evenly, weakly concave along median half of margin. S6 with midapical truncation one-fifth width of sternum, truncation slightly wider than deep, apical margin of truncation very weakly emarginate midapically (Fig. 47; S6 sometimes folded along longitudinal length, thus increasing appearance of midapical emargination); S6 with lateral edge strongly folded, bulbous in appearance in ventral view. Gonoforceps strongly swollen subapically, apical to swelling with flattened, narrowed process (Figs 45, 46, 49-51).

Distribution.

Canada from Yukon, the Northwest Territories, and Nunavut southeast to Ontario and Quebec.

Holotype male.

"[Canada] Norman Wells, N.W.T. [Northwest Territories], 13-VII-1949, W.R.M. Mason// Holotype male Osmia nearctica Rightmyer, Griswold, & Arduser" (Ottawa)

Paratypes.

CANADA: MANITOBA, Winnipeg Capitol Region, Kettle Rapid, nearWinnipeg, 14 July 1917 (1♀, New York); NORTHWEST TERRITORIES, Dehcho Region, Hay River, 5 June 1951, P. R. Ehrlich (2♀, Ottawa); Inuvik Region, Reindeer Depot, MacKenzie Delta, 23 June 1948, W. J. Brown (1♀, Ottawa), 16 July 1948, J. R. Vockeroth (1♀, Ottawa); Sahtu Region, Norman Wells, 19 May 1953, C. D. Bird (1♀, Ottawa), 27 May 1953, C. D. Bird (1♀, Ottawa), 12 June 1949, W.R.M. Mason (2♀, Ottawa), 3 July 1949, W.R.M. Mason (1♀, Ottawa), 4 July 1949, W.R.M. Mason (1♀, Ottawa); NUNAVUT, Kitikmeot Region, Coppermine, 3 August 1951, S. D. Hicks (1♀, Ottawa); ONTARIO, Thunder Bay District, Black Sturgeon Lake, 13 June 1961 (1♂, Ottawa); QUEBEC, Nord-du-Québec Region, Rupert River, 10 July 1956, J. R. Lonsway (1♂, Ottawa); YUKON, Dempster Highway km 465, 15 July 1982, D. Wood (1♀, Ottawa).

Etymology.

The name “nearctica” is derived from the Greek arktikous, meaning northern or arctic, and is in reference to the known distribution of this species in northern regions of the New World (i.e., Canada).