Basiceros browni Probst & Brandão, 2022

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 : 13-16

Basiceros browni Probst & Brandão sp. nov.

( Figs 2C , 3 , 4 , 30 )

Type material. Holotype worker: ECUADOR: Los Ríos (spelled as “ Pichincha ”): 47km N from Quevedo, Rio Palenque Research Station , 29.vii.1978, G.J. Umphrey col., N. GJU # 0860 [ MCZ] . Paratype workers: Same locality, date, and collector as holotype [ MCZ, one gold coated worker; GUPC, one worker]; same locality and collector, 30.vii.1978 [ NMH, one worker (NHM1014338/ CASENT0900941 )]; Pichincha: Otongachi , 0°18’49” S 78°57’15” W, 850m, 04.ix.2009, G. Ramón col., KT-1419/LL8-W15 [ MZSP, one worker] .

Diagnosis (only known from workers). Comparatively medium to large (TL 6.55–7.59 mm); color light brown to dark brown; densely sculptured, rugose to areolar-rugose, procoxae and gaster foveate; petiole tubuliform, without projected node; mandibles triangular, long and pedunculate with twelve teeth on each masticatory margin; clypeomandibular space ample; labrum cuneiform, bilobed apically, lobes separated by a narrow cleft; pilosity consisting of a basal layer of flat and spatulate to subplumose decumbent curved hairs for most of their length, and another layer of long erect and clavate hairs.

Description. Worker (n=4, range includes holotype measurements). HL 1.25–1.41, HL2 1.29–1.45, HW1 1.16– 1.33, MdL 0.8–0.9, SL1 0.93–1.13, SL2 0.90–1.15, PDL 4.5–6, A3L 0.04–0.05, AFL 0.38–0.45, FuL 1.04–1.21, EL 0.15–0.18, EW 0.14–0.16, ML 1.7–2.0, MfL 1.40–1.68, MtL 1.08–1.25, PH 0.32–0.35, PL 0.87–0.97, PW 0.32–0.38, PPL 0.45–0.52, PPW 0.47–0.55, GL 1.47–1.77, GW 1.06–1.16, TL 6.55–7.59, CI 93–95, CS 1.21–1.37, MCI 62–64.00, SI 76–86, ESI 15–16, SAI2 240–255, EI1 0.24–0.25, MFI 77–85, PTI 266–291.

Size comparatively large compared to other Basiceros species. Light brown to dark brown, with lighter appendages, yellowish-brown to brown, respectively. Body predominantly covered by two types of hair. White to light brown semi-erect to erect hairs, long and filiform and slightly clavate, present on head dorsum near eye height and extending to occipital region, sparsely present on ventral region of head; on the anterolateral corner and dorsum of pronotum; a pair present on the anterodorsal margin of propodeum; on sides and petiolar dorsum; on the dorsum of postpetiole, two pairs on the anterior margin of postpetiolar sternite; on the dorsal and ventral gastral margins, more abundant dorsally. Length of these hairs varying according to position, notably longer on the dorsal surface of entire body. White to yellowish decumbent hairs, flattened, short and curved, apically spatulate or subplumose, present on the head dorsum, pronotum and propodeum, more densely on the latter. One pair of spatulate hairs on the basal portion of lateroventral region of mandibles and another on the base of stipes, relatively close to the hypostomal margin. Setae sparse, from simple and short to apically spatulate, at the base of mandibles. Long and erect spatulate hairs on the anterior margin of antennal scapes, scape dorsa covered by short spatulate hairs, filiform setae on the inner face of the antennal basal lobe, hair on the scape elbow (anterior region of lobe) with the same morphology as the special hairs present on the rest of the body. Clypeal disc with short and appressed setae. Filiform and apically curved hairs present on the pygidium and hypopygium. Short and subdecumbent spatulate hairs on trochanters and tibiae and on posterior region of tarsi, becoming thinner on the distal segments.

Mandibles smooth over most of its length and shiny, with sparse piligerous punctuations, interdental filiform setae present, surpassing length of the teeth; anterior region striated. Clypeus rugo-reticulate in great part of its central disc; lateral regions predominantly areolar-rugose, anterior region of clypeus laminar, smooth and shiny, with its anteromedial portion weakly covered by longitudinal striate impressions. Head dorsum covered by thick and irregular striae, gaps between them forming foveae of variable size. Internal surface of antennal scrobes. Ventral face of head punctuate-reticulate, changing to rugose near posterior margin and roof of antennal scrobes; extending posteriorly to the vertexal margin, covering this region and the sulcus present near the median region. Vertexal region scrobiculate around the occipital carina. Mesosoma strongly sculptured, dorsum covered with vermicular rugae ranging from strongly irregular in the dorsum of the promesonotum to obliquely longitudinal in the dorsal region of the propodeum; lateral region of the pronotum and central portion of mesopleuron punctate-reticulate; mesopleuron with sinuous lamellar epicnemial carina bordered by sparse scrobiculations; lateral region of propodeum with irregular and transversally vermiculate striae, forming foveae of variable size, varying to punctate-reticulate in its central range and becoming rugose again near the bulla of the metapleural gland; posteropropodeum covered by sparse punctuations, varying to longitudinal rugulae as the sloping face advances to the propodeal lobes. Petiole and postpetiole with oblique to irregular longitudinal rugae. Posterior region of the petiole longitudinally rugulose. First gastral segment densely punctuate-reticulate; punctuations intermediate and distinct, with smooth and shiny space between them; punctuations decreasing near the posterior margin, thinner and more reticulate. Other gastral segments with exposed tergites finely reticulate—same to sternites, but with margins and shinier. Procoxae punctuate-reticulate, meso- and metacoxae punctuate to dotted to irregularly rugulose; legs with inconspicuous rugo-reticulations.

Head subtrapezoidal, with posterior margin slightly convex medially; mandibles long and peduncular, masticatory margins with 12 triangular teeth, apex of basal tooth comparatively more rounded and apical tooth wider; clypeomandibular space present, semi-spherical. Labrum cuneiform, bilobed apically; lobes separated by a very narrow or even slightly inconspicuous cleft. Clypeal disc flat, anterior margin lamellar, slightly convex in its median range. Palps hidden. Antennal scrobes shallow, with indistinct posterior limit. Antennal scapes long (SL 0.90–1.15) and slightly tubular; basal lobe short and trapezoidal; anterior margin crenulated and laminar; funicular segments gradually increasing in size, two-segmented apical club present with the apical segment being as long as the sum of the five anterior funicular segments and slightly shorter than half the length of scape (AFL: 0.38–0.40; SL1 0.93–1.00). Compound eyes rounded and convex, located just above the posterior half of the head (in frontal view) and at the limit of the anterior margin of the scrobes (lateral view), with about nine ommatidia in the largest diameter. Vertexal margin slightly concave, with a shallow groove in its median portion; posterolateral edges angulate, not protruding. Occipital carina present, not projected.

Lateral profile of mesosoma with promesonotum convex, sloping posteriorly into a broad and deep metanotal suture. Propodeal profile slightly convex posteriorly. In dorsal view, humeral corners projected and rounded; promesonotal suture indistinct to weakly marked; promesonotum slightly wider than twice the propodeum. Sloping face of the propodeum anteriorly delimited by a superior transverse carina that connects to the propodeal spines, those divergent in dorsal view and oriented upwards, presenting a strong carina in the region of convergence with the slope. Propodeal spiracle tubular, opening circular. Metapleural gland bulla prominent; posterolateral region carinate, opening surrounded by cuticular flap. Propodeal lobes short and rounded. Tarsal claws simple. Petiole in lateral view long and tubular; smooth and sloping anterior surface, meeting the dorsal surface obtusely; dorsal face convex, with an anterior portion lower than the median portion; in dorsal view, peduncle long, petiole with anterior face ellipsoid, posterior face slightly narrower and marginally rounded, subpetiolar process composed of an anteroventral oblique and bifid projection, followed by 4–7 spiniform projections of different sizes, the first or second sometimes denticular and the first sometimes protruding from the base of anterior anteroventral process. Postpetiole longer than wide; wider and higher posteriorly; in dorsal view, anterior margin concave. In lateral view, postpetiolar sternite carinate; in ventral view, present a pair of carinae in parallel with the lateral limits of this sclerite. Sting conspicuous.

Gyne, male, and larva: unknown.

Etymology. named after Dr. William (Bill) Brown Jr., reference for the taxonomy of “basicerotine” ants.

Comments. Basiceros browni sp. nov. can be separated from other Basiceros by the combination of a tubuliform petiole, without a projected node; long and pedunculate mandibles with a wide clypeomandibular space; labrum shape (cuneiform, lobes separated by narrow cleft); and general pilosity (long, erect, and clavate hairs).

This new taxon was initially recognized from stacked macrophotographs of a worker specimen on AntWeb, deposited at the NHM in London. The label contained a handwritten note indicating it as a paratype (although this species was yet to be formally described) of the species “ Basiceros browni sp. nov. ”. Thanks to the aid of Dr. Brian Fisher (Cal Academy) in identifying the collector origin, the specimen was linked to Dr. Gary J. Umphrey, professor in the Department of Statistics at the University of Guelph, Ontario, Canada. Dr. Umphrey kindly traveled to the FMNH in Chicago with some Basiceros specimens. Among the workers of this new taxon that Dr. Umphrey made available for examination, one was coated for SEM and missing the left proleg. For those specimens, considerable variation in size could be noted (in mm: HL 1.25–1.41, ML 1.70 –2.00, GL 1.47–1.77, TL 6.55–7.59). Additionally, specimens presented slight variation in the distal margin of labrum, with the cleft in one specimen practically indistinct. The lighter coloration of one of the workers and the absence of particles covering its integument suggest a recently emerged worker, selected to be the holotype.

Distribution. So far, only known from the provinces of Pichincha and Los Ríos in Ecuador from two collection events (1978 and 2009, respectively). The specimens collected at the Río Palenque Research Station have “ Pichincha ” as the province; this reserve is instead located in the Province of Los Ríos.

Natural history. Virtually nothing is known about the biology of this species. The first collection resulted in four workers; three workers retrieved on July 29, 1978 from a rotten log at the edge of a trail in the middle of a forest. According to Dr. Umphrey, the nest was not found. The last 1978 specimen was collected the following day while foraging about three meters from the place occupied by that rotten log, suggesting it might have been part of the same colony. The paratype collected in Otongachi came from a Winkler sample.

Figures

FIGURE 2. Morphological measurements of Basiceros species; A. lateral view of worker and B. dorsal view of alate gyne of B. conjugans (MCZ546461, Peru: 15 km NE Puerto Maldonado), EL: Eye Length, PDL: Pedicel Length, AFL: Apical Flagellomere Length, ML: Mesosoma Length (= Weber’s Length), MTL: Metatibia Length, PTH: Petiole Height, PTL: Petiole Length, PPL: Postpetiole Length, MSL: Mesoscutum Length, MSW: Mesoscutum Width, MLL: Mesoscutellum Length, MLW: Mesoscutellum Width, MFL: Metafemur Length, PTW: Petiole Width, PPW: Postpetiole Width, GW: Width of gaster. C. full-face view of Basiceros browni sp. nov., paratype worker (MZSP, Ecuador: Pichincha, Otongachi), HL: Head Length, HL2: Head Length 2, HW1: Head Width 1, MdL: Mandible length, SL1: Scape Length 1, SL2: Scape Length 2, FuL: Funiculus Length. D. full-face view of male of B. manni (MCZ, Costa Rica: Heredia), HW2: Head Width 2, LOD: Lateral Ocellus Length, MOD: Median Ocellus Length, OOD: Oculo-ocellar distance, A3L: Antennomere 3 Length. Figures not to scale.

FIGURE 3. Basiceros browni sp. nov., holotype worker (MCZ, Ecuador: Los Ríos); A. full-face view, B. lateral view, and C. dorsal view.

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

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