Proplebeia tantilla, CAMARGO & GRIMALDI & PEDRO, 2000

CAMARGO, JOÃO M. F., GRIMALDI, DAVID, A. & PEDRO, SILVIA R. M., 2000, The Extinct Fauna of Stingless Bees (Hymenoptera: Apidae: Meliponini) in Dominican Amber: Two New Species and Redescription of the Male of Proplebeia dominicana (Wille and Chandler), American Museum Novitates 3293, pp. 1-1 : 1-

Proplebeia tantilla , new species

Figures 10 , 15–21

DIAGNOSIS: The male is distinguished from that of P. dominicana , mainly by flagellomeres wider than long, median projection of S6 without apical emargination, and gonostyli swollen and with a hairy, solelike area at apex. Worker is easily distinguished from P. dominicana and P. vestusta by small body size (2.1, 3.0–3.2, 4.4 mm, respectively), presence of relatively long, straight hairs on sterna, and long microtrichia over veins M + Cu and first abscissa of M. Proplebeia tantilla is very similar to P. dominicana and the small Plebeia (s.s.) in the general form of the head, mesosoma, and metasoma.

DESCRIPTION: Male (AMNH­DR­14­1439). Dimensions: Approximate body length 2.52 mm, forewing length from apex of costal sclerite to wing tip 1.90 mm (including tegula 2.24 mm; wing seems slightly shortened due to striations in the amber); maximum head width 1.04 mm. Color of integument: Predominantly black, lacking yellow marks; chestnut on ventral part of metasoma, legs, tarsomeres, labrum, mandibles except condyles, maxillar galeae and tegulae; wing veins honey­colored, membrane hyaline. Pilosity: Pale yellow over entire body. Decumbent, plumose, pale, minute hairs relatively sparse on face; some erect hairs on clypeus (0.06 mm long); vertex with unbranched erect hairs up to 0.14 mm long. Mesoscutum practically devoid of micropilosity, only some sparse erect hairs, the longest ones on anterior corners ca. 0.08 mm on scutellum ca. 0.16 mm long; on ventral part of mesepisterna up to 0.12 mm long. Basal area of propodeum glabrous. Posterior edge of tibia III with unbranched hairs (ca. 0.14 mm long). T1­3 glabrous; T4­6 with some hairs on sides, T7 with some unbranched hairs up to 0.20 mm long. S2­4 with only one hairy band, S5 with a row of short hairs on median portion of apical margin (0.04 mm), S6­7 apparently lacking hairs. Integument: Smooth and shiny, except for some sparse piligerous punctures; slightly rugose on superior part of head. Form and proportions: Head 1.24× wider than long (1.04: 0.84, length measured from apex of clypeus to upper tangent of median ocellus). Eyes 1.9× longer than wide (0.72: 0.38) and convergent below; upper interorbital distance 0.56, maximum distance 0.58, lower distance 0.38. Malar area linear. Clypeus trapezoidal, 1.7× wider than long (0.34: 0.20), slightly convex; labrum normal, slightly convex. Distance between clypeus and median ocellus (0.54) practically equal to the upper interorbital distance. Interalveolar distance nearly equal to the diameter of antennal alveolus and ca. 2× longer than the alveolorbital distance (0.11: 0.12: 0.06). Frons with median line impressed well. Distance between lateral ocelli 2.0× diameter of median ocellus and 2.4× ocellorbital distance (0.22: 0.11: 0.09). Vertex very narrow, with abrupt slope behind lateral ocelli; preoccipital ridge slightly rounded. Scape length ca. 3.5× its diameter (0.28: 0.08), and ca. 2 ⁄ 3 distance between antennal alveolus and lateral ocellus (0.42 mm). Flagellum plus pedicel (1.04) ca. 3.7× length of scape; flagellomeres shorter than wide (the second one, 0.08: 0.10). Scutellum not visible in dorsal view, in profile slightly projected beyond metanotum. Forewing 2.04× longer than wide (1.90: 0.93; the wing may be slightly shortened due to striations in the amber; this distortion could not be corrected by application of glycerin and a coverslip); pterostigma 4× longer than wide (0.40: 0.10); marginal cell 4.37× longer than wide (0.70: 0.16), slightly open at apex; Rs slightly sinuate toward apex; angle between Rs and Rs + M slightly open; first abscissa of M ca. 5 ⁄ 7 length of first abscissa of Cu (0.30: 0.42), and a little shorter than Rs + M + second M (0.32). First submarginal cell without clear limits, entirely open. Hamuli, 5. Tibia III subtriangular, 3.08× longer than wide (0.80: 0.26); posterodistal corner angled slightly open. Basitarsus III 2.15× longer than wide (0.28: 0.13), with anterior margin practically straight and posterior margin slightly sinuate; posterodistal corner right angled. S2­4 unmodified; S5 invaginated, but apparently with slight emargination on each side of median distal border; S6 with one long, median, spatulate projection turned downward, and deeply emarginate on each side; S7 very wide and strongly sclerotized. Genitalia triggered, with penis covering part of the structures; penis valves short, about half of the length of gonostyli and strongly arched; gosnostyli relatively short and swollen at apex, forming a hairy, solelike area on inner surface; no structure visible that can be interpreted as a spatha (details of genitalia and pregenital sterna in fig. 20).

Worker (AMNH­DR­14­911). Specimen very deformed due to dehydration in amber (e.g., antennae completely flattened, ocelli pedunculate), so measurements provided here do not reveal real size of body structure; only wings are apparently unaltered. Dimensions: Approximate body length 2.1 mm; forewing length from apex of costal sclerite to wing tip 1.96 mm (including tegula 2.26 mm); maximum head width 0.96 mm. Color of integument: Predominantly black, with several parts of the body discolored and translucent. There are no perceptible yellow markings on head; clypeus and supraclypeal area chestnut (discolored?); lower parocular areas lighter; scape yellowish, discolored; flagellum dark chestnut; mandibles discolored (translucent). Mesosoma black, lacking yellow markings, only anterior corners of mesoscutum discolored. Legs strongly discolored and translucent; only posterior distal border of tibia III and whole basitarsus III blackish. Forewing C and R veins distinctly black; pterostigma largely translucent in middle; wings membrane hyaline; microtrichia dusky. Metasomal terga blackish; sterna discolored. Pilosity: Fine, decumbent, minute hairs covering whole face as in Plebeia (s.s.), clearly plumose on lower parocular areas; less perceptible on clypeus. Vertex with some erect, unbranched, pale hairs, longest ones ca. 0.12 mm. A fine layer of bubbles on integument hinders observation of micropilosity on mesoscutum; however, pale and sparsely distributed erect hairs are quite visible; on anterior corners they are denser and as long as ones on vertex. Distal border of scutellum with some very long unbranched hairs, ca. 0.18 mm. Microtrichia sparse, clearly visible in radial and cubital cells and in area corresponding to first submarginal cell of forewing (fig. 10), longest ones ca. 0.02 mm; denser and shorter toward wing apex; veins M + Cu and first abscissa of M with some long hairs (ca. 0.03 mm), black, clearly visible. Sterna, mainly S3, with very long, erect hairs, T1–2 apparently glabrous dorsally, T3–4 with some erect hairs; T5 and especially T6 with erect very long, unbranched hairs, the longest ones ca. 0.16 mm. Posterior border of tibia III, with unbranched hairs ca. 0.16 mm long; one corbicular hair 0.20 mm long; basal third of tibia with some erect hairs 0.10 mm long, all pale yellow. Penicillum with very long (ca. 0.20 mm) hairs; posterior parapenicillum with two visible hairs, largely bent, ca. 0.20 mm long. Positions of legs preclude observation of details of the keirotrichiate area and presence of a rastellum; only right tibia III observable with two long hairs (ca. 0.07), which might belong to rastellum. Left leg measurements possible for only the length of some hairs of keirotrichiate area (ca. 0.03 mm). Integument: Smooth and shiny, as in P. dominicana . Form and proportions: Although measurements do not correspond to exact size of structures (except for wings), some are given below which might provide useful proportions: maximum head width 0.98; upper, maximum, and lower distances 0.65, 0.67, 0.52, respectively; eye length 0.68; clypeus width 0.36; length of pedicel plus flagellum 0.76; scape 0.32; malar area length 0.08; mandible 0.80, with two denticles on inner corner of apical cutting edge, space between them semicircular. General form of head as in the small species of Plebeia (s.s.). Labium ca. 1.20 mm long (glossa only 0.48), completely translucent. Mesosoma very deformed, but apparently similar to those of P. dominicana and Plebeia (s.s.); scutellum normal, in an approximately equilateral arch with round apex, without basal fovea. Tibia III subtriangular (as in P. dominicana and Plebeia , s.s.), elongate, with posterodistal corner acutely angled, strongly projected (tibia is very compressed, approximately 0.20 wide). Forewings folded and cannot be measured; pterostigma 3.6× longer than wide (0.36: 0.10); marginal cell a little more bulging at base than in P. dominicana (0.64: 0.20), and more open apically; angle between Rs and Rs + M slightly acute, ca. 85°; first abscissa of M 1.35× longer than Rs + M + second M (0.38: 0.28); free portion of Cu vein imperceptible; submarginal cell entirely open, lacking any trace of vein that delimits it. Hamuli, 5. Metasoma short, triangular; last tergum pointed apically.

TYPES: Holotype, male, AMNH­DR­14­ 1439 , in Miocene amber of the Dominican Republic. Fragments of one male and fragments of one worker in the same amber piece are paratypes. One worker in an additional piece, AMNH­DR­14­911 , with same origin, is also a paratype. Exact mine where amber was found is unknown.

ETYMOLOGY: From the Latin, tantillus, little, small.

REMARKS: Another male of the same species, sectioned longitudinally during polishing of the piece by Dominican dealers is included in the same piece of amber with the holotype (AMNH­DR­14­1439). What remains are the ventral portion of the mesosoma, part of the metasoma, genitalia and legs; there are also fragments of the maxillae, labium, mandible and legs of one worker, supposedly of the same species. In the fragment of tibia III, which corresponds to the distal half, it is possible to see the rastellum with at least seven long (cylindrical?) hairs (fig. 18), as in P. dominicana ; the penicillum and anterior parapenicillum are well developed but it is not possible to see details; in the distal half of the inner surface, the posterior glabrous rim, about 2 ⁄ 7 the keirotrichiate area width, is apparently not depressed. In Nogueirapis silacea the depressed area is limited to the basal half of the tibia ( Wille, 1959), and in P. dominicana the step does not follow the contour of the keirotrichiate area and is gentler toward the apex of the tibia (fig. 4). The worker (AMNH­DR­14­ 911) was interpreted as P. tantilla based on the body size, and the shape and size of the wing veins; it was not possible, however, to verify if the male has long microtrichia on veins M + Cu and the first abscissa of M, as in the worker.

The male of P. tantilla differs from that of P. dominicana mainly by having flagellomeres wider than long, the median projection of S6 not apically emarginate, penis valvae short and slender, and gonostyli swollen at the apex, forming a hairy, solelike area (an autapomorphic condition). There are no shared apomorphies among male characters, only S7 is well developed and sclerotized in both species (but this can be a plesiomorphic condition; in modern genera S7 is usually reduced and weakly sclerotized). The decision to include this species in the genus Proplebeia was based on characters of the worker: rastellum with 7–8 long, spinelike hairs, and glabrous posterior rim of inner surface of tibia III very wide, ca. 2 ⁄ 7 the width of keirotrichiate area, although it is not clear if the rim is depressed and forms a step.

Figures

Figs. 8–10. Forewing, worker; 8. Proplebeia vetusta, sp.n., holotype, specimen, AMNH­DR­14­854; 9. Proplebeia dominicana, specimen AMNH­DR­14­1175; 10. Proplebeia tantilla, sp. n., paratype, specimen AMNH­DR­14­911. Scale = 1.0 mm.

Figs. 15–19. Proplebeia tantilla, sp. n. 15–17. holotype, male, AMNH­DR­14­1439, head, forewing, and tibia and tarsus III. 18, 19. paratype, worker, same amber piece, fragments of tibia and tarsus III, detail of rastellum, and mandible, detail of denticles.

Fig. 20. Proplebeia tantilla, sp. n., holotype, male, AMNH­DR­14­1439, detail of pregenital sterna and genitalia, ventral view.

Fig. 21. Photomicrograph of Proplebeia tantilla, sp. n., male, holotype, AMNH­DR­14­1439. Scale = 1.0 mm.