Basiceros singularis ( Smith 1858 )

Probst, Rodolfo Da Silva & Brandão, Carlos Roberto Ferreira, 2022, A taxonomic revision of the dirt ants, Basiceros Schulz, 1906 (Hymenoptera, Formicidae), Zootaxa 5149 (1), pp. 1-75 : 56-59

Basiceros singularis ( Smith 1858)

( Figs 23–25 , 30 )

Meranoplus singularis Smith 1858 (in part): 195, Plate 13, Figs 8–10 (worker; gyne probably of Basiceros scambognathus , see Brown & Kempf 1960: 175): Brazil.

Combination in Ceratobasis: Smith 1860: 78 .

Combination in Basiceros: Wheeler 1916: 9 .

Wheeler 1916: 9 (gyne);

Kugler 1978: 438, Figs 43–49 (sting apparatus)

Brown 1974: 140 (male diagnosis).

Wheeler & Wheeler 1977: 599, Fig 9 ( Basiceros sp. larva = B. singularis )

Wheeler & Wheeler 1980: 537, Fig 4 (larva).

Type material. BRAZIL: Amazonas : Ega (=Tefé): no data, no collector ( Meranoplus singularis , one worker — lectotype) [ MNH] (examined) .

Diagnosis. Very similar to B. manni . Comparatively large; coloration light brown to brown. Double layer of specialized pilosity distributed as a basal layer of subdecumbent plumose hairs and a layer of fine erect and clavate hairs. In general, specimens densely covered with soil and/or litter particles. Clypeomandibular space ample; anterodorsal region of mandibles and clypeus dorsum usually with squamiform pilosity. Petiole claviform, elongate and with a depressed node. Anterior margin of first gastral sternite medially elevated, with a longitudinal projection in the form of a carina or prominence.

Description. Worker (n=5). HL 1.29–1.31, HL2 1.43–1.56, HW1 1.09–1.43, MdL 0.90–0.95, SL1 1.18–1.22, SL2 1.19–1.25, PDL 0.12–0.15, A3L 0.03–0.06, AFL 0.47–0.50, FuL 1.19–1.31, EL 0.19–0.25, EW 0.15–0.21, ML 2.05–2.37, MfL 1.72–1.89, MtL 1.37–1.56, PH 0.40, PL 1.06–1.15, PW 0.243–0.47, PPL 0.53–0.64, PPW 0.59–0.67, GL 1.81–1.97, GW 1.25–1.44, TL 7.65–8.40, CI 84–109, CS 1.19–1.37, MCI 69–72, SI 87–108, ESI 15–20, SAI2 253–250, EI1 0.29–0.34, MFI 63–76, PTI 261–282.

Large size compared to other Basiceros . Coloration (when integument is visible, not densely covered with particles) brown to light brown; appendices slightly lighter. Mandibles with same coloration as appendages, slightly reddish-brown; dorsum with tiny piligerous punctuations close to the masticatory margin, remaining surface either covered by coarse piligerous punctuations with squamiform, slightly whitish decumbent or irregularly and superficially rugose; mandibular apex with short yellowish setae; interdental setae present, yellowish and brush-shaped, slightly longer than teeth. Basimandibular seta present, narrow and erect, located at the anteroventral limit of mandibular peduncle. Stipes covered by fine, medium and subdecumbent pilosity; suberect clavate hair on its dorsum close to anterior margin. Labrum densely covered with piligerous punctuations: short, decumbent and squamiform setae. Dorsal surface of clypeus covered by coarse piligerous punctuations, with decumbent, short and squamiform yellowish hairs. Head dorsum predominantly covered by piligerous fovea, pilosity squamiform or with plumose aspect, subdecumbent; long erect to suberect hairs sparse on the anterior portion of head and more abundant near the posterolateral region and vertexal margin. Ventral surface of head covered by piligerous punctuations; hairs long and erect close to head sides and as line on head center, and by squamiform hairs marginating the ventral limit of antennal scrobes. Pilosity on meso- and metasoma as a double layer of specialized hairs. Basal layer composed of yellowish and subdecumbent plumose hairs, more abundantly than on B. manni , as follows: dense, surrounding the anterior margin of pronotum; a little more sparse on pronotum and mesonotum dorsa, on dorsum and lateral of propodeum, on mesopleuron flange near the epicnemial fossa, on the upper portion of mesopleuron, on dorsal surface of petiolar and postpetiolar nodes; petiolar peduncle with plumose hairs on its side; densely covering the postpetiole sternite; gaster pilosity with hairs with plumose aspect and squamiform hairs, relatively sparse; on anterior face and anterolateral portion of procoxae and on the dorsum and anteroventral margin of all coxae. The second layer is composed of erect to suberect hairs, distributed slightly more sparsely than on B. manni , long and slightly apically, present on the meso- and metasoma as follows: dense on the dorsal surface of pronotum, petiolar node, postpetiole and gaster (on the ventral portion, relatively sparse on the anterior region of first segment); one pair present on the metanotal suture; three pairs on the dorsum and sides of propodeum; slightly thinner and sparse on petiolar peduncle; two pairs on each side of the anterior margin of postpetiole sternite; present on the anterior face and anterolateral portion of procoxae; two to three pairs on the dorsum of meso- and metacoxae. Femora and tibiae covered by short subdecumbent hairs, with a flattened aspect on tibiae. Appressed and clavate minute hairs also present on these segments, more easily recognized on the ventral surface of femora, tibiae and basitarsi of all legs. Antennal pilosity unique: subdecumbent squamiform hairs on the basal lobe of scape, dense hairs, erect to suberect on scape dorsum; external margin with long erect hairs and slightly swollen medially, distributed along the crenulation; short and apically curved hairs also following the external margin; ventral face with short, subdecumbent setae; funiculus densely covered with short, decumbent setae.

When it is possible to observe the integument, it is mostly smooth and shiny on glabrous regions. Dorsum of mandibles and clypeus covered by punctuations or rugae. Anteroventral portion of mandibles slightly alveolate. Dorsal surface of labrum finely reticulate. Head irregularly rugose, rugae forming foveae of different sizes; antennal fossa reticulate; antennal scrobe surface punctuate-foveate on its posterior half; ventral face of head granulose-punctuate, punctuations coarse and slightly overlapping. Anterior and lateral margins of pronotum foveate. Mesonotum with lateral costulae, extending to the anterolateral surface of propodeum, the latter with coarse punctures. Petiolar peduncle finely reticulate-punctuate. Gaster densely punctuate-reticulate; tergite of abdominal segments V, VI and VII finely and densely punctuate, slightly opaque, tergal margins smooth and shiny, slightly yellowish; sculpture slightly sparser on first gastral sternite, especially anteromedially. Antennal scapes finely rugo-reticulate. Coxae punctuate-foveate, other leg segments superficially rugo-reticulate.

Head oblong, lateral emarginate from eye height to posterolateral region and behind the head; posterior portion of head slightly depressed, projected posteriorly; vertexal margin with rounded corners, less divergent in the posterior portion than observed for B. manni , median portion largely concave. Occipital margin narrower than that of B. manni , cervical margin wide, lamelliform and conspicuously transversely carinate. Palp formula 2,2; palps strongly fused; maxillary palp slightly larger and wider than labial, with a sensillum; labial palp apically clavate, with two sensilla. Stipes subrectangular. Labrum lunate, arched laterally; round, anterior margin continuous. Mandibles triangular; in full-face view, lateral margins slightly concave; basal margin conspicuously concave leaving a wide clypeomandibular space; basal angle round, followed by about 18 denticles, slightly serrated and gradually decreasing in size along the masticatory margin; in lateral view, mandibular apex slightly curved ventrally. Clypeus lamellated laterally and on anterolateral portion; anterior margin medially concave. Compound eyes developed. Coarse ruga in front of eyes, projecting from the middle of antennal fossa limit and extending to head side like an arc. Antennal scape with slightly rounded lamellar basal angle, outer margin crenulate and lamellar. Antennal fossa deep. Antennal scrobe deep on anterior half, posterior and ventral limit weakly distinct.

Mesosoma slender; lateral profile of promesonotal complex continuously convex, strongly sloping caudad; metanotal suture wide. Mesopleuron anteriorly bordered, interrupted at the meeting with a narrow epicnemial fossa. In lateral view, anterior portion of propodeum short and slightly oblique posteriorly, dorsal surface of propodeum slightly sloping posteriorly. Propodeal declivity laterally carinate and with strong transverse lamellar carina connecting the short, sharp and tapered propodeal projections. Opening of propodeal spiracle round. Metapleural gland bulla protruding, prominent; opening transverse and covered by cuticular lamella. Petiolar peduncle longitudinally carinate on its dorsal surface. In lateral view, petiole claviform, petiolar node obsolete, conspicuously low; dorsal margin bulging; postpetiole subcircular, subequal to petiolar node. Subpetiolar process extremely variable: from short anterior spiniform process followed or not by short spines to the most diverse combinations of bifid processes, lamella, simple spines and vestigial processes of different sizes. In dorsal view, petiolar node ogive-shaped; posterior margin of postpetiole convex, widely inserted to anterior concavity of gaster. Postpetiolar sternite conspicuously carinate anteromedially, prora present, lamellar and slightly darkened. Gaster with yellowish lamellar anterodorsal margin; anteroventral margin of the sternite keeled or carinate medially (this character is sometimes hindered by particle covering). Although it is not possible to notice a gastral sulcus like the one found on B. manni , the central longitudinal band of the first gastral tergite is entirely glabrous. Calcar of strigil pectinate. Meso- and metabasitarsi conspicuously long, about ¾ of tibial length. Tarsal claws simple. Sting apparatus (after Kugler, 1978): wide, spiracular plate ovoid, anterior apodeme subtriangular. Body shortly extended to medial connection. Spiracle small, near center of plate. Quadrate plate: apodeme and body narrow and reduced; anterodorsal corner with digitiform process, well sclerotized; plate gradually reduced ventrad, especially apodeme. Oblong plate not divided into preincision and post-incision; dorsal crest as wide as length of posterior arm; arm not on midline; transversely broad, anterior apodeme spatulate; ventral arm short and broad; fulcral arm narrow, continuously tapering from base; vertical. Gonostylus: sclerites well-defined; only trichoid and chaetoid sensilla present; proximal segment tapering from base. Triangular plate: elongated; prominent apicoventral process. Lancet: sword-shaped; single valve relatively large, but not very developed; sulcus converging to ventral crest. Sting: blade slightly longer than the sum of the lengths of the bulb and the valve chamber, gently curved upwards and moderately sclerotized; valve chamber slightly shorter than the sting bulb; sting base moderately arched and obliquely truncated in lateral view. Basal notch short and heavily arched; articular processes short and slightly directed to ventral margin. Sting bulb large; sides straight and gently converging. Furcula: T-shaped, extremities of lateral arms extending slightly over sting bulb.

Gyne (n=3). HL 1.35–1.40, HL2 1.0–1.44, HW1 1.06–1.14, MdL 0.90–0.91, SL1 1.15–1.18, SL2 1.13–1.18, PDL 0.14–0.15, A3L 0.05, AFL 0.45–0.48, FuL 1.16–1.26, EL 0.25, EW 0.23–0.24, LOD 0.08, MOD 0.06, OOD 0.37–0.38, ML 2.13–2.15, MSL 1.00–1.05, MSW 0.8–0.82, MLL 0.25–0.3, MLW 0.4–0.42, MfL 1.70–1.71, MtL 1.38, PH 0.32–0.42, PL 1.00–1.07, PW 0.3–0.42, PPW 0.52–0.57, GL 1.92–1.95, GW 1.32–1.35, TL 7.93–8.00, CI 77–84, CS 1.22–1.25, MCI 65–66, SI 103–105, ESI 21–22, SAI2 250–257, EI1 0.38–0.40, MTI 76–82, MLI 141–160, MFI 62–66, PTI 235–330. (In bold measurements influenced by accumulation of litter and soil particles on the integument).

Coloration and sculpture similar to conspecific workers; slightly larger size. Cephalic dorsum with three ocelli: median ocellus inserted at the height of posterior limit of compound eyes and lateral ocelli inserted slightly above. Head pilosity as in conspecific workers. Double layer of specialized pilosity on pronotum denser than in workers. Basal pilosity more sparsely present on the mesoscutum and mesoscutellum. Median portion of metanotum with a pair of long, clavate and suberect hairs, and four hairs on the basal layer with a plumose appearance.

Basal pilosity present on posterior corner of mesoanepisternum, just below forewing insertion. Ventral and posterior limits of mesokatepisternum with basal pilosity, as well as ventral portion of metakatepisternum. Pilosity on rest of body with shape and configuration similar to conspecific workers. Mesoscutum with irregular longitudinal rugae, interposed with rugulae forming foveae of different sizes. Mesoscutellum irregularly rugo-foveate. Mesopleuron irregularly rugose, sparse punctuation within foveae formed by these rugae. Anapleural sulcus granular, submedian transverse carina present. Anterior portion of petiolar peduncle finely reticulate. Lateral of mesoscutellum striate-reticulate. Metanotum finely reticulate. Gastral sculpture stronger impressed than on workers. Sculpture of other regions as in conspecific workers. In dorsal view, humeral angles strongly projected, dividing the pronotum into two regions. Mesoscutum slightly cuneiform, anteriorly round, with a short, smooth and subopaque longitudinal carina on its anteromedial portion; slightly cuneiform; posterior margin broadly convex at the meeting with the scutoscutellar suture. Notauli and parapsidal lines indistinct; parapsides slightly deep, subreniform; tegulae narrow, elongated and somewhat translucent, apical margin round. Pre-scutellum narrow; axillae projected posteriorly, round and slightly depressed. Sulcus scutoscutellar well-marked, with transverse costulae. Mesoscutellum trapezoidal, posterior limit concave; in lateral view, one the same level as or just below the scutum. Anapleural sulcus wide, matte, and transversal to body axis. Sting developed. Forewing type 1; hindwing with 5–8 submedian hamuli.

Figures

FIGURE 4. Basiceros browni sp. nov., paratype worker (GUPC, Ecuador: Los Ríos); A. full-face view, B. lateral view, and C. dorsal view.

FIGURE 8. Basiceros convexiceps, worker (MZSP, Brazil: São Paulo); A. full-face view, B. lateral view; C. dorsal view. Scale bars: A = 0.5 mm, B–C =1 mm.

FIGURE 9. Basiceros convexiceps, gyne (MZSP, Brazil: São Paulo). A. full-face view, B. lateral view; C. dorsal view. Scale bars: A = 0.5 mm, B–C =1 mm.

FIGURE 10. Basiceros convexiceps, larva (from type-series of Basiceros squamifer) (MZSP, Brazil: Rio de Janeiro) and male forewing diagram (adapted from Emery, 1924) (Brazil: Santa Catarina); A. Head in ventro-oblique view, B. head in oblique view, C. male forewing (black arrow highlights transversal 1m-cu vein), D. anus, E. thorax in lateroventral view, highlighting the spinose pilosity, F. lateral view. Scale bars: A, B–E = 0.1 mm; F = 0.5 mm.

FIGURE 23. Basiceros singularis, worker (CASENT0914890, Ecuador: Napo); A. full-face view, B. lateral view, C. dorsal view. Images by Michele Esposito (CAS), edited.

FIGURE 24. Basiceros singularis, gyne (MCZ 534402/T2-56, Trinidad & Tobago: St. Andrew) and male (MCZ, Trinidad & Tobago: St. Andrew); A and D. full-face view, B and E. dorsal view, C and F. lateral view. Scale bars: A, D = 0.5 mm, B, C, E, F =1 mm.

FIGURE 25. Basiceros singularis intercastes from Trinidad & Tobago: St. Andrew; A–D: MCZ534402/T2-56); A. lateral view of mesosoma, white arrow pointing to wing fossa and wing trace, B. lateral view, C. dorsal view highlighting mesoscutum line (white arrow) and wing trace (black arrow), D. dorsal view; E–H: (MCZ/T2-56); E. oblique view of mesosoma, white arrow pointing to vestigial hindwing, F. lateral view, G. dorsal view highlighting rudiments of a mesoscutum (left white arrow), mesoscutellum (right white arrow), and forewing trace (black arrow), H. dorsal view. Scale bars: 1 mm.

FIGURE 30. Distribution map of Basiceros species from the singularis clade.