Osmia (Diceratosmia) lacunosa, Griswold & Rightmyer, 2017

Rightmyer, Molly G., 2017, A revision of the subgenus Osmia (Diceratosmia), with descriptions of four new species (Hymenoptera, Megachilidae), Zootaxa 4337 (1), pp. 1-37 : 16-17

Osmia (Diceratosmia) lacunosa new species

( Fig. 4A )

Diagnosis. Males of the very small species O. lacunosa (intertegular distance 1.4 mm) are unique among known species of Diceratosmia in the shape of the scutellum ( Fig. 4A ): the anterior margin forms two triangular processes, forming three pockets (one median and two lateral) in the suture between the mesoscutum and mesoscutellum. In other Diceratosmia , the anterior margin of the scutellum may be straight or gently biconvex, but never forms such distinctly triangular processes. Osmia lacunosa is additionally distinguished from all other Diceratosmia except O. stangei by the carinate omaulus. Osmia lacunosa and O. stangei , both Caribbean species, can be distinguished from each other by the shape of the axillae (unmodified in O. lacunosa , emarginate in O. stangei ), relative lengths of F1 and F2 (F1 nearly half F 2 in O. lacunosa ; subequal in O. stangei ), and patch of hairs found medially on the apical margin of S3 (broad and only slightly surpassing apical margin of S 3 in O. lacunosa ; narrow and well surpassing apical margin of S 3 in O. stangei ). See the Diagnosis of O. stangei for further comments on these characters.

Description. Female. Unknown.

Male. Total length: ca. 6.5 mm; Forewing length: 5 mm; distance between lateral ocellus and preoccipital margin: 0.4 mm; distance between lateral ocellus and compound eye: 0.3 mm.

Color: Integument clear cerulean blue, except brown on mouthparts, labrum, apical half of mandible, apical edge of clypeus, antenna, posterior half of tegula, inner surfaces of legs distal to femora, basally on S3–S4, S5–S8; brown with bluish overtones on basal half of mandible, inner surfaces of legs basal to tibiae and entire outer surfaces of legs, anterior surface of T1, apical margins of metasomal terga, S1–S2, apical margins of S3–S4. Wings moderately infuscate, leading edge of forewing more strongly infuscate.

Pubescence: White, minutely branched hairs on body except slightly more plumose on face, hypostomal area, and mesosoma; longer, simple to minutely branched hairs interspersed on legs (especially outer surfaces of basitarsi), and T3–T7 laterally; short, dense bands of white tomentum apicolaterally on T1–T2; stouter, pale golden hairs on inner surfaces of all tarsi; short, sparse, minutely branched hairs on discs of metasomal terga; short, simple, dense on discs of S3–S4. Labrum covered with branched hairs on apical half, hairs forming short fringe at apical margin. S3 medially on apical margin with dense tuft of posteromedially directed hairs (hairs ca. 1 OD in length). S4 subapical margin (i.e., transverse band, ca. apical one-fifth of disc) uniformly covered on all punctate areas with minutely branched, suberect hairs, these hairs not interrupted medially on S4. S6 largely hairless.

Punctation: Head with punctures ovate to circular, contiguous to separated by half puncture diameter, deeply impressed, with scattered, sparse micropunctures between larger punctures except as follows: labrum mostly impunctate on basal third; clypeus with apical truncation impunctate for about one-half length of F1 or slightly less; hypostomal area near angle with punctures weakly impressed. Mesosoma with punctures round to ovate, separated by 0.2 to 1.0 puncture diameter, deeply impressed, with scattered, sparse micropunctures between larger punctures except as follows: tegula with punctures minute, sparser on posterior two-thirds, separated by up to eight puncture diameters; metepisternum weakly shagreened; pronotum, metanotum, propodeum, and propodeal triangle very strongly shagreened to granulose, dull (strongly contrasting with shiny scutellum); metanotum with punctures small and sparse (separated between two and four puncture diameters); pronotum and propodeum with punctures weakly impressed; propodeal triangle lineolate on dorsal fourth to fifth; propodeal pit parallel-sided, slit-like; legs with punctures on outer surfaces more irregular, more weakly impressed, with inner surfaces of trochanters, femora, and tibiae shiny to weakly shagreened, with scattered smaller punctures. T1 with anterior surface shagreened; metasomal terga with dorsal surfaces between punctures shiny. Metasomal terga with punctures round, well impressed, separated by 0.2 to 1.0 puncture diameter, with scattered micropunctures between larger punctures (T4–T7 with punctures slightly sparser, slightly less distinct and circular). T1–T3 with small impunctate apical margins (ca. one adjacent puncture diameter); T4–T5 and T7 apical margins with sparse, small punctures and overlying hairs; T6 with apical impunctate margin slightly thickened, about one to two adjacent puncture diameters in length. S1–S2 and S4 medially on apical margin with well impressed, circular punctures, S3 on extreme lateroapical margin and S4 subapically along width with punctures present but poorly impressed, not well defined. S5–S6 weakly shagreened, with scattered small punctures.

Structure: Maxillary palpus four-segmented; labial palpus with second segment ca. 1.5x longer than basal segment. Mandible with outer and condylar ridges converging apically; with two teeth, upper tooth very slightly shorter and wider than lower tooth; inner margins of upper and lower teeth forming nearly 80 degree angle; upper tooth with inner and dorsal margins forming ca. 45 degree angle; inner, ventral margin of mandible carinate apically, weakly diverging away from condylar ridge. Clypeus with distinct truncation medially on apical margin, lateral corner of truncation forming ca. 140 degree angle with lateral margin of clypeus. Inner margin of antennal socket weakly carinate, raised dorsomedially and slightly overhanging socket. Interantennal area and frons clearly elevated above level of paraocular area. Flagellar segments subequal in length, except F1 half F2 length, F11 nearly one-fourth longer than other segments. Vertex behind lateral ocellus ca. 2.0 OD in length. Genal width three fourths compound eye width in lateral view or slightly more. Preoccipital margin rounded, not carinate. Hypostomal carina moderately high, very slightly higher midway along length of proboscidial fossa, shorter at angle, not forming distinct tooth. Pronotal lobe and omaulus with strong carinae separating anterior and lateral surfaces. Scutellum with triangular medial and lateral notches in the anterior margin, forming three pockets (one median and two lateral) at the suture between the mesoscutum and mesoscutellum. Malus forming triangular apical spine about same size as adjacent margin of velum, inner margin of spine with minute hairs. Foretarsal segments 2–3 with anterior lobes distinctly longer than posterior. Mid and hindtarsi not swollen. Hindtibial spurs moderately curved at apical sixth, outer spur slightly shorter than inner. Hind basitarsus relatively long, slender, with lateral margins of outer surface parallel, lacking tooth on inner margin. T6 medioapical margin with small impunctate truncation, this truncation very weakly concave along width. T6 lateroapically with triangular tooth (apex rounded); lateroapical margin of T7 somewhat recessed, not continuous with apical margin of medioapical impunctate truncation. T6 lateroapical tooth larger than T7 submedian tooth. T7 midapically with shallow emargination, forming ca. onefourth of circle in outline, with teeth on either side of emargination very small, triangular). S2 widely, weakly subtruncate, medially nearly straight; disc of S2 overhanging much of S 3 in repose. S3 apical margin evenly, weakly convex, lacking emargination; S3 carinate subapically on extreme lateral corner. S4 apical margin laterally with carinae forming posteriorly directed trough, medially ventral-most carina reduced to obsolescence where punctures overlay medioapical margin. S5 apical margin only partially visible, but apparently shallowly, widely emarginate. S6 apical margin strongly convex, not forming distinct truncation. S8 apical margin triangular. Gonoforceps strongly swollen subapically, with distinct secondary projection arising from inner apical margin (more distinctly visible in lateral view); this secondary projection apically swollen; gonoforceps more or less straight along length in lateral view.

Distribution. Known only from Allans Cay, Commonwealth of the Bahamas ( Fig. 18 ).

Floral Associations. None.

Holotype male. “[ Commonwealth of the Bahamas] Abaco Cays, Allans Cay , May 9, 1953 // Van Voast— A.M. N.H . Bahamas Isls. Exped., Coll. E. B. Hayden // HOLOTYPE Osmia lacunosa Griswold & Rightmyer ♂ HOLO75 [red label]” (NEW YORK) .

Etymology. This species is named after the Latin word “lacuno”, meaning hollowed out or pit, in reference to the three pits on the anterior margin of the scutellum.

Figures

FIGURE 4. Dorsum of mesosoma showing posterior half of scutum, scutellum and axilla: A) male O. lacunosa (HOLO 75), B) female O. stangei (BBSL 989171). Scale bar = 0.25 mm.

FIGURE 18. Known distributions of O. conjunctoides (green triangles), O. exquisita (white circles), O. gonzalezi (red circles), O. lacunosa (yellow circles), O. spinulifera (blue circles), and O. stangei (purple triangles). Scale bar = 200 km.