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Extracted from: Molly G. Rightmyer1, Terry Griswold1, Michael S. Arduser. 2010. A review of the non-metallic Osmia (Melanosmia) found in North America, with additional notes on palearctic Melanosmia (Hymenoptera, Megachilidae) ZooKeys 60: 3777 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,
O. maritima, are given under that species (see above).
In the Palearctic, O. nearctica is most similar to O. 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) (O. 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
(O. 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
fl ange that curves away from the condylar ridge (O. xanthomelana with the
lower margin of the mandible opaque, forming a ridge that is parallel to the condylar
ridge). Th e hairs of the mesepisternum tend to be dark brown in O. nearctica,
while in O. xanthomelana the hairs tend to be pale yellow to white, and the hairs
of the hypostomal area tend to be denser in O. nearctica than in O. xanthomelana. In males, the propodeal triangle is weakly shagreened throughout in O. nearctica
(Fig. 41) (O. 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 O. nearctica (in O. 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 O. nearctica (Fig. 43) than in O. xanthomelana;
the S6 midapical truncation is clearly emarginate in O. nearctica (Fig. 47)
(O. xanthomelana with S6 truncation not emarginate); and the apical tip of the gonoforceps
(apical to subapical swelling) is more rounded in O. nearctica (Figs 49, 50) (in
O. xanthomelana the apical tip is more pointed). Osmia nearctica can be diff erentiated
from O. maritima and O. alticola by the microscopic hairs on the underside of thefl agellar segments (O. maritima and O. alticola with conspicuous hairs about half the
width of the fl agellar segments). Description. Female. Figs 9, 10, 3338. Total length: 9.011.5 mm; forewing
length: 6.57.2 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, fl agellar segments, legs, and apical margins of
Figures 6470. 64, 65. Osmia maritima, male, genital capsule 64 Dorsal view 65 Lateral view. 6668.
Osmia steinmanni, male paratype. 66. Dorsal view of genital capsule 67 S3 and S4 68 S5 and S6 69, 70
Osmia svenssoni, male paratype. 69 Dorsal view of genital capsule 70 S4 and S6.
A review of the non-metallic Osmia (Melanosmia) found in North America, with additional... 69
T1T5. 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, 0.20.5 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, 3.04.0
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; T1T3 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 2.04.0 puncture diameters in length. T4T5 dorsal
surfaces shagreened, weakly shining, excluding apical impunctate bands with punctures
nearly contiguous to separated by 2.0 puncture diameters; apical impunctate
bands about 5.08.0 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), fi rst tooth longer than other teeth, length
between apical tips of second and fourth teeth subequal to slightly wider than apical
tips of fi rst 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 fl agellar segments gradually increasing in length such that F10 subequal
to F1 or little longer. Vertex behind lateral ocellus 2.02.5 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 fi fth shorter than inner.
Hind basitarsal segment with lateral margins of outer surface parallel. Male. Figs 3951. Total length: 8.6 mm (8.09.1 mm); forewing length: 6.0 mm
(6.06.5 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, fl agellar segments, legs, and apical margins of T1T6
and S1S3. 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 fi lling entire
emargination (hairs ca. 1.0 OD in length medially, 2.0 OD laterally) (Fig. 44). S4 with
weakly defi ned, 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 twothirds;
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 fi ve 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; T1T2
with dorsal surfaces excluding apical margins weakly shagreened, shining; T3, T6T7
dorsal surfaces moderately shagreened; T4T5 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. 4.05.0 puncture diameters in length
(sometimes medially as long as 6.07.0 puncture diameters in length). T2T7 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; T2T6 with apical impunctate
margins 4.08.0 puncture diameters in length, T7 lacking apical impunctate margin.
S13 with punctures minute, well-impressed, nearly contiguous to separated by ca. 1.0
puncture diameter. S4S6 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 1.52.0 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-fi fth 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 defi ned midapical truncation (Fig. 44). S5 with apical
margin evenly, weakly concave along median half of margin. S6 with midapical
truncation one-fi fth 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 fl attened, narrowed
process (Figs 45, 46, 4951). Distribution. Canada from Yukon, the Northwest Territories, and Nunavut
southeast to Ontario and Quebec. Etymology. Th e 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).
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