A taxonomic revision of the dirt ants, Basiceros Schulz, 1906 (Hymenoptera, Formicidae) Author Probst, Rodolfo Da Silva 0000-0002-5885-5701 probstrodolfo@gmail.com Author Brandão, Carlos Roberto Ferreira 0000-0002-5885-5701 probstrodolfo@gmail.com text Zootaxa 2022 2022-06-02 5149 1 1 75 journal article 53922 10.11646/zootaxa.5149.1.1 caecca9d-72a3-4d9a-836d-9ac3e0ded512 1175-5326 6605961 BF98000F-04F9-4D22-9D93-4C3A2418D7EF Basiceros tumucumaquensis Probst & Brandão sp. nov. ( Figs 26–28 , 32 ) Type material. Holotype worker : BRAZIL : Amapá , PNMT , 1.242333 -52.419778 ± 10m , 132m , 25.xii.2018 , R . Probst & O. Guilherme cols. ( R . S. Probst #678) [ MZSP , CASENT0647157 ] . Paratype workers : Same data as holotype [ MZSP , 4 workers , CASENT0647158 , CASENT0647159 , CASENT0647160 , CASENT0647161 ; MPEG , 2 workers , CASENT0647162 , CASENT0647163 ; DZUP , one worker , CASENT0647164 ; MCZ , one worker , CASENT0647165 ; JTL , one worker , CASENT0647166 ] . Paratype male : Same data as holotype [ one male , MZSP , CASENT0647167 ] . Diagnosis. Mandibles bizarre, apical portion strongly curved ventrally, basidorsal sulcus present, slightly transversal to mandibular dorsa, basal angle translucent. Clypeus densely covered with decumbent squamiform hairs. Head dorsum rugulose, with long clavate hairs. Descriptions. Worker (n=5, range downward from size of smallest to biggest individual. Includes holotype , 3 paratypes , and a non-type each from Amapá and Rondônia). HL 1.28–1.44, HL2 1.22–1.47, HW1 1.04–1.24, MdL 0.48–0.58, SL1 0.97–0.99, SL2 1.02–1.08, PDL 0.09–0.11, A3L 0.03–0.04, AFL 0.385 –0.409 , FuL 0.95–1.02, EL 0.09–0.12, EW 0.09, ML 1.556–1.7, MfL 1.28–1.35, MtL 1.0–1.06, PH 0.32–0.35, PL 0.74–0.76, PW 0.29–0.33, PPL 0.51–0.54, PPW 0.51–0.538, GL 1.54–1.71, GW 1.04–1.12, TL 6.2–6.63, CI 81–85, CS 1.16–1.31, MCI 40– 42, SI 84–97, ESI 9–11, SAI2 3011–3347, EI1 0.15–0.16, MFI 81–91, PTI 213–234. Medium size comparatively. Coloration reddish-brown to brown; appendages lighter. Mandible dorsa covered by minute sparse piligerous punctuation, bearing erect to suberect setae; basal portion with clavate pilosity suberect to subdecumbent; mandibular apex with medium yellowish setae. Basimandibular setae present, narrow and erect. Clavate suberect hairs on the dorsum of each stipe. Anterior margin of labrum with long filiform hairs. Clypeal dorsum densely covered with decumbent squamiform hairs. Head with basal layer of hairs with similar morphology as clypeal pilosity (although longer), sparse and located at margin of sculpture; erect and slightly clavate pilosity as follows: one pair on frons, close to the median head depression, one pair on the temple, around the sulcus of vertexal margin, a pair present anterior to and a pair near the posterior limit of eyes; several on vertexal corners and superficial emargination projected above the eyes until the vertexal margin. Mesosoma, petiole, postpetiole, and first gastral sternite with basal pilosity suberect to sudecumbent, slightly clavate to clavate. Erect to suberect pilosity on mesosomal dorsum, petiole and postpetiole, coxae, and gaster; relatively abundant, clavate, yellowish; pygidium with short, filiform, suberect hairs. Antennal scapes mainly with yellowish suberect clavate hairs; funiculus covered by short, appressed, and yellowish setae. Tibiae and femora with abundant subdecumbent clavate pilosity, tarsi with subdecumbent setae. Surface of antennal scrobes matte, finely strigulate; head dorsum rugulose, median temple punctate. Pronotum laterally punctuate-reticulate; anterior portion rugulose. Surface of mesopleuron and propodeum matte, rugulae sparse. Petiole and postpetiole rugulose. Procoxae areolate-rugulose. Gaster densely areolate-punctate. Head oblong; posterolateral corners round; vertexal margin slightly raised medially. Vertexal crest present, shallow; sulcus around head visible; temple medially depressed. Mandibles aberrant, trapezoidal; external margin slightly concave; masticatory margin straight bearing 10–11 teeth, apical tooth slightly broader and longer; apical portion of mandibles strongly curved ventrally to the midpoint of their length; basal angle strongly convex, portion translucent; in full-face view, sulcus present on basal portion, extending from the masticatory margin to at least half of the lamina, slightly transversal. Labrum short and triangular, overall shape similar to B. scambognathus (see Figs 2E and 3E from Probst et al . 2019 and Fig 27B–C ); lateral lobes short, distal margin with cleft extending slightly longer and more slit-like than on B. scambognathus . Frontoclypeal surface convex; anterior margin medially concave. Tumosity present on frons, circular-shaped and with central concavity. Eyes inserted on the dorsal margin of antennal scrobes, these deep and extending posteriorly to the vertexal margin. Scape flattened and with a biangulate basal lobe, margin between angles concave; external margin lamellar and crenulated. Antennal apical segment slightly longer than the sum of three anterior antennomeres. Mesosoma robust; in lateral view, promesonotal profile slightly convex dorsally; metanotal suture strongly impressed, extending as the anapleural sulcus, transversely rugulose. Propodeum posteriorly oblique; propodeal projections short, triangular and slightly upwards, connected by strong transverse carina; propodeal spiracle elliptic, spiracle directed posteriorly. Petiole nodiform, peduncle short; node anteriorly oblique and strongly tapered posterad. Subpetiolar process consisting of series of long sharp denticles. In lateral view, postpetiole slightly longer than length of petiolar node; slightly dorsoventrally flattened, dorsal face slightly projected on its posterior half, posterior margin bulged at the meeting with gaster. In dorsal view, petiolar node slightly oblong, ogive-shaped; anterior margin of postpetiole strongly concave, posterior margin convex. Gaster oval; anterior margin concave; first gastral sternite visibly longer than tergite. Metabasitarsus conspicuously long, longer than metatibia. Tarsal claws simple. FIGURE 26. Basiceros tumucumaquensis sp. nov. holotype worker (MZSP, CASENT0647157, Brazil: Amapá); mandibles in A. dorsal view, B. oblique view, C. lateral view, D. ventral view, highlighting ventrolabrum, E. dorsal view, F. lateral view, G. full-face view, H. oblique view of head and pronotum. Scale bars: A–D = 0.2 mm, E–F = 1 mm, G–H = 0.5 mm. Male . (n=1) HL 1.072, HW1 0.954, HW2 1.113, MdL 0.431, SL2 0.21, PDL 0.118, A3L 0.387, AFL 0.63, EL 0.347, LOD 0.11, MOD 0.083, OOD 0.396, ML 1.78, MSL 1.009, MSW 0.85, MLL 0.32, MLW 0.552, MfL 1.469, MtL 1.023, PH 0.36, PL 0.8, PW 0.317, PPL 0.474, PPW 0.462, GL 1.627, GW 1.17, TL 6.18, CI 88, CS 1.01, MCI 40, SI 22, ESI 165, SAI 54, SAI2 33, EI1 0.63, EI2 85, MTI 84, MLI 172, MFI 64, PTI 222. Coloration black, with areas slightly ferruginous (e.g., propodeal lobes and scutoscutellar sulcus). Coxae and central portion of femora dark, rest of appendages lighter, yellowish. Pilosity primarily composed of long filiform whitish hairs covering the body, mainly head, dorsum of promesonotum, and sparser on gaster. Wigs brown, microtrichia dense. Integument matte, with a grainy aspect. Head covered with irregular rugulae, punctuate in between; mesosoma dorsally rugulose. Mesokatepisternum rugulose, mesoanepisternum rugulose-punctate, other integument covered by dense rugulose-punctate sculpture that resemble reticulate punctuations on lower magnification. Mandibles sinuous, elongated; rugulose. Masticatory margin with 10 short triangular teeth, second and third teeth from the base slightly broader than others; apical tooth falcate; external margins of mandibles convex. Head subpiriform, cervical flange conspicuous. Antennal torsion conspicuous. Ocelli large and positioned on cephalic crest; median ocellus inserted after a transversely rugose cleft. As for other Basiceros males, a deep concave sulcus is present along the frontoclypeal region. Central disc of clypeus convex, central portion raised; anterior margin and lateral portions slightly depressed. Anterior clypeal margin slightly concave medially, lateral margin convex. Eyes globular, large, and shiny. Antennal fossa deep. In dorsal view, mesoscutum slightly cuneiform anteriorly, as wide as long; anterior margin with smooth and shiny median carina, extending along dorsum of mesoscutum but not reaching notauli, these lightly impressed. Scutoscutellar suture broadly concave. Parapsides oval, slightly deep. Parapsidal lines smooth and shiny. Scutoscutellar sulcus broad and deep, transversally costulate. In dorsal view, mesoscutellum transversely rectangular, longitudinally divided by a median posterior sulcus. Propodeal projections round, propodeal lobes auricular and slightly narrow. Petiole and gaster similar to conspecific females. Subpetiolar projection absent, only obsolete spine on peduncle present; petiolar spiracle slightly projected laterally. Forewing type 2; hindwing with five submedian hamuli. Gyne and larva . unknown. Etymology. The species name tumucumaquensis is masculine and a Latin singular adjective in the Nominative, paying homage to the Tumucumaque Mountains National Park (PNMT), type locality and protection area named after the Tumuc-Humac mountain range in the states of Pará and Amapá . The PNMT is Brazil’s largest national park and one of the world’s largest protected tropical forests. FIGURE 27. Basiceros tumucumaquensis sp. nov. paratype worker (MZSP, CASENT0647158, Brazil: Amapá); A. full-face view, D. dorsal view, E. lateral view. Labrum from non-type worker (MZSP, Brazil: Rondônia); B. dorsal view and C. ventral view; lo: lateral lobe, black arrow: specialized seta on anterior margin. Crossed arrows give the orientation: a, anterior; p, posterior. Scale bars: A = 0.5 mm, D–E =1 mm, B–C = 0.1 mm. Comments. Basiceros tumucumaquensis sp. nov. can be separated from other Basiceros by the combination of mandibular and labrum morphologies and general pilosity on the worker, and by head and mandibular morphologies, pilosity, and mesosomal sculpture on the male. This new species is very similar to B. scambognathus , from which the worker caste can be differentiated based on head shape and pilosity, body pilosity, mesosomal and gastral sculpture, and mandibular shape. The male of this new species looks like a chimera between males of B. conjugans , B. manni , and B. scambognathus . Body coloration is almost uniformly dark; mandibles are sinuous and not subtriangular like in B. scambognathus ; the apical tooth follows the profile of the masticatory margin, not being projected as in B. scambognathus ; the head is subpiriform, resembling other males of Basiceros —in B. scambognathus , it is subhexagonal. In terms of variation, workers of B. tumucumaquensis present slightly variations in integumentary coloration and sculpture, pilosity density, and subpetiolar process, size, and slightly on labrum morphology—the cleft on distal margin can vary on extension and inner margin of lateral lobes can be more or less straight. The holotype and some paratypes had oribatid mites on the ventral face of mandibles. It is not possible to confirm whether such arachnids are phoretic, commensal myrmecophiles or parasites. FIGURE 28. Basiceros tumucumaquensis sp. nov. paratype male (MZSP, CASENT0647167, Brazil: Amapá); A. head and antenna, B. lateral view, C. full-face view, D. dorsal view. Scale bars: A–B, D =1 mm, C = 0.5 mm. Distribution. North and NW South America. Currently known from the PNMT, the state of Rondônia , and potentially from a forest fragment close to Manaus, state of Amazonas (Itanna Oliveira, pers. comm., material not examined). This species occurs in sympatry with its sister taxon B. scambognathus , and hints of cryptic variation came from two workers collected in Rondônia (included in the phylogenetic analyses from Probst et al ., 2019 ). At that time, those two workers (BSCJ1 and BSCJ2) were considered to be populational variations within B. scambognathus —so much that Probst (2015) included photographs of one of those workers under B. scambognathus . The boundaries of B. scambognathus started to make more sense after the phylogenetic study of Basiceros ( Probst et al . 2019 ; see Fig 5 ), which recovered B. scambognathus as two sister clades. One clade grouped three male specimens from Amazonas (North of Brazil ), Minas Gerais (Southeast of Brazil ), and Peru ; the other clade grouped those two workers from Rondônia (west of the Amazonian biome). In the same study, Probst et al . (2019) pointed out the unique morphology of these two workers in terms of pilosity patterns, head, and body shape, and suggested that they may correspond to a cryptic species within B. scambognathus . Supported by phylogenetic information from Probst et al . (2019) and by studying additional specimens, we raise it here as a new species. Natural history. Virtually nothing is known about the biology of this species. The type-series was collected below surface, close to tree roots, with the nest apparently scattered in indistinct chambers. RSP also collected two workers from a leaf litter sample taken around superficial roots of a Brazil nut tree ( Bertholletia excelsa , Lecythidaceae ). Those two workers were kept alive in laboratory conditions for three days, in which sparse interactions between specimens were observed. Workers moved slowly through the terrarium, with occasionally slowpaced antennation and showing thanatosis when disturbed. Unfortunately, all the conducted “cafeteria” experiments failed and specimens did not accept any items offered. Similarly, part of the type-series was kept alive in laboratory conditions for several weeks, consistently ignoring live prey dropped inside the terrarium, but sometimes accepting freshly-killed adult fruit flies. Material examined. BRAZIL : Amapá , PNMT , 1.242333 -52.419778 ± 10m , 132m , 25.xii.2018 , R . Probst & O. Guilherme cols. (additional 20 non-type workers, several broken and/or dissected) [ RSPPC ] ; Rondônia : Porto Velho , Área Mutum 09°34’49”S 65°03’13”W , 15–30.vii.2013 , R . S. Probst & G. R . Mazão cols. ( 2 workers ) [ MZSP ] .