Basiceros scambognathus (Brown) Feitosa & Brandão & Dietz, 2007

Feitosa, Rodrigo Machado, Brandão, Carlos Roberto Ferreira & Dietz, Bodo Hasso, 2007, B (Brown, 1949) N. Comb., With The First Worker And Male Descriptions, And A Revised Generic Diagnosis (Hymenoptera: Formicidae: Myrmicinae), Papéis Avulsos de Zoologia (São Paulo) 47 (2), pp. 31-42 : 35-41

Basiceros scambognathus (Brown) n. comb.

( Figs. 1‑4 )

Creightonidris scambognatha Brown, 1949:89 . Holotype gyne, BRAZIL: Goiás, Campinas, x.1935 (Schwarzmeier) ( MZSP) [examined]. Brown & Kempf, 1960:178, figs. 5, 8, 10 (genus revision, type locality); Kempf, 1972:80 (catalogue); Lattke, 1991:59 (record in Venezuela); Bolton, 1995a:1049 (census); Bolton, 1995b:146 (catalogue); Delabie, 2000:272 (distribution); Bolton, 2003:184 (synoptic classification); Castilho et al., in press. (distribution); new combination.

Meranoplus singularis Smith, 1858:195, pl. 13, figs. 6, 7 (only the gyne). Holotype gyne: BRAZIL: Amazonas: Tefé (formerly known as Ega), no date, (no collector) [not examined].

Ceratobasis singularis Smith, 1860:78 , pl. 4, figs. 12, 13 (only the gyne).

Worker: HW 1.13; HL 1.25, CI 92.31; ML 0.46; SL 0.96, SI 83.33; WL 1.52; HFL 1.30; TL 6.00. Color dark brown, appendages somewhat lighter; mesopleuron, petiolar peduncle and gaster with ferruginous areas. Mandibles smooth and shining with minute scattered punctures; inner surface of antennal scrobes with transversal rugulation over fine punctuation; surface of head rugulose, the rugae forming a loose net with deep cells, with whole integument finely punctuated; lateral face of pronotum and anterior coxae with gross punctuation, pronotal disc with punctuation and loose net of rugulae; mesopleuron, metapleuron, petiolar node, postpetiole and surface of the gaster feebly shining and rather smooth, with abundant punctures. Dorsum of head, laterobasal mandibular area, mesosomal dorsum, petiole, postpetiole and first gastral sternite with small, whitish, subapressed and apressed spatulate hairs; hairs dense on head and antennal scapes, less abundant on mesosoma, waist and gaster; appendages with abundant cream‑colored subapressed spatulate hairs directed apically and becoming gradually finer towards tarsi; posterior part of head, dorsum of mesosoma, posterolateral corner of pronotum, abdominal segments II‑VII with fairly abundant short, erect, strongly clavate whitish‑golden hairs; distinct group of long filiform hairs project from labrum; pygidium with short erect hairs.

Head subtriangular. Mandible long and subtriangular; external margin of basal portion almost parallel; apical portion slightly longer than the basal one, external border strongly convergent with the apex of the other mandible, and nearly straight masticatory border; apical portion almost perpendicularly bent ventrad at mid‑length; basal portion moderately convex in side view; a deep transverse‑oblique, convex groove almost divides the basal mandibular disc in two, running from the masticatory margin to at least halfway across the mandible and ending shallowly there, the grooves converging with the groove in the opposing mandible at the juncture of the two masticatory borders to form a broad V with an obtuse, posteriorly directed, apex. Central disc of clypeus convex, its anterior border very shallowly and broadly emarginate or concave; anterior portion of head capsule deeply impressed compared with clypeus, forming two transverse‑oblique grooves deeper anterad and meeting apically to form a broad inverted V. Triangular area indistinct, glabrous; no space between clypeus and mandibles when closed. Central portion of cephalic dorsum raised as large circular swelling with deep concavity in center forming thick ring. Posterior head margin with shallow and broad medial concavity; occipital lobes rounded and slightly projected. Eye relatively small (ca five facets at maximum diameter) and placed far back, just on the dorsal margin of antennal scrobe; scrobe deep, running full length of cephalic side; scape flattened and strongly lobed basad by projection of anterior margin, apical segment of funiculus longer than four preceding segments.

Mesosoma robust, promesonotum only moderately convex dorsally; anepisternum set lower than the adjacent surface; metanotal groove deeply impressed; propodeal spines very short and subtriangular; propodeal spiracle wide open, relatively projected laterad and directed posteriorly.

Petiole pedunculate, slightly arched, with a prominent and thick node which is nearly longer than the peduncle, node with steep anterior and gently sloping postero‑dorsal faces, peduncle ventrally carinate with a series of small, acute projected denticles. Postpetiole subequal in length to the petiolar node, low in profile with a long, flat, sloping dorsal face which raises to a low rounded apex posteriorly and then drops slightly to its juncture with the gaster; seen from above, the petiole is narrower than postpetiole and is oblong in shape, while the postpetiole is subtrapezoidal, as broad behind as long, the sides diverging posteriorly and then very slightly narrowed so that it is attached to gaster by nearly its entire breadth. Gaster long and oval, its anterior border semicircularly excised to receive the postpetiole; first gastric segment forming the great bulk of the gaster.

Gyne: Holotype (n=3): HW 1.25 (1.16‑1.24); HL 1.42 (1.34‑1.42), CI 88 (87); ML 0.42 (0.39‑0.41) MI 30 (29); SL 1.09 (1.04‑1.09), SI 87 (88‑90); WL 1.84 (1.85‑1.88); HFL 1.30 (HFL 1.28‑1.31); TL 7.00 (6.93‑7.03). Like worker, with the modifications expected from myrmicine gynes. A complete description of the gyne was given by Brown (1949) in the original description of Creightonidris . Additional information is given above in the reviewed diagnosis of Basiceros .

Male: (n=4): HW 0.87‑1.00; HL 1.04‑1.15, CI 84‑87; ML 0.20‑0.23, MI (0.19‑0.20); WL 1.63‑1.87; HFL 1.23‑1.37. Color dark brown with somewhat ferruginous areas. Body sculpture basically rugosepunctate, except for central discs of anepisternum and katepisternum which are smooth and shiny; head covered with scattered irregular rugae; alitrunk with sparse rugae on dorsal surface of promesonotum, inferior portion of mesopleuron, propodeum and petiole; broad punctures shallowly set on lateral surfaces of alitrunk and waist, but slightly finer on gaster. Long filiform whitish hairs cover body, densely arranged on head, dorsum of promesonotum and gaster.

Mandibles triangular, as broad as long, stout with 10 subconical teeth, the third and fourth ones broader than the others; apical tooth directed outwards and slightly distant from subapical one; external margins of mandibles strongly convex at basal portion and straight to nearly concave towards apex. Head rounded in shape. Ocelli placed almost laterally in the median elevation of occipital border, central ocellus preceded by deep cleft. A deep groove is present along posterior border of clypeus at space between eyes. Central disc of the clypeus raised and forming distinct circular area, lateral portions somewhat lower, anterior margin straight to slightly concave. Eyes very large. Antennal scrobes shallow and limited posteriorly by high nucal carina.

In dorsal view, prescutum nearly as broad as long; notauli shallowly impressed; antero‑median portion of prescutum with a smooth and shining triangular area; parapsidial furrows extending beyond prescutum mid‑length; parapsides broad and relatively deep; prescutellum visible medially in dorsal view; lateral wings of prescutellum subtriangular, with acute and well developed postero‑lateral hook; scuto‑scutellar groove broad and deep with 2‑4 transversal rugae; scutellum twice as broad as long and divided by longitudinal groove medially. Propodeum bluntly angulated in side view, not bearing teeth or lamellae.

In lateral view, petiolar node subrectangular with rounded angles; in dorsal view node is rounded; subpetiolar spines varying from present and small to virtually absent. Postpetiole subtrapezoidal with posterior border convex and broader than anterior one. Gaster long and oval.

Comments

The aberrant mandible and depressed anepisternum of Basiceros scambognathus separate this species from the related Basiceros singularis . Originally, B. singularis was described by Smith (1860) based on a worker and a gyne. However, the gyne is a typical B. scambognathus , while the worker seems to be unrelated as judging from the figures (the type specimens are lost). This situation was only solved with the description of the genus Creightonidris by Brown in 1949, when he provided further details.

In the description of the holotype gyne, the value of TL is stated as being 7.4 mm; Brown & Kempf (1960) made an amendment to this measure stating that the specimen has the gaster dilated in around 0.4 mm; thus, the value here presented should be considered the correct measure.

A complete diagnosis of Basiceros was given by Brown & Kempf (1960) and Brown (1974). In the present paper we offer a supplement to the latter in order to include the features of B. scambognathus n. comb. We add information regarding the shape of the head and mandibles, and describe in more detail the structure of the gyne’s mesosoma.

All apomorphies of the Basicerotini defined by Bolton (2003) hold true for the specimens of B. scambognathus we examined.

Unfortunately we were aware of recent material collected by colleagues only during the final revision process of the present paper. They were: a gyne collected at Nossa Senhora do Livramento county , northern Pantanal in Mato Grosso, Brasil, and the worker collected in a secondary Atlantic Forest area in Lençóis, Bahia, Brasil (12°33’S 41°23’W) (Castilho et al. in press). Both specimens were obtained from leaf litter samples using Winklers extractors .

Distribution

Until now, B. scambognathus was known only from the Brazilian largest biomes (Amazon Forest, Cerrado, and Atlantic Forest) and for a single locality in south Venezuela, near the border with Brazil (see map in Fig. 4 ). Its apparently discontinuous distribution and scattered records may reflect inappropriate collecting techniques due to our ignorance of the species biology.

Biology

B. scambognathus is one of the most obscure taxa of neotropical ants and virtually nothing is known about its biology. Very few specimens are represented in the world’s ant collections, most of them are alate gynes and males, captured in widely spaced localities.

Brandão collected the first dealate B. scambognathus gyne in Uruaçú, Goiás state, in 1995, and attempted to maintain it in artificial conditions in order to obtain workers or males and to record its behavior. Unfortunately, the specimen died some weeks after confinement and the only piece of information we were able to gather is that the captive gyne accepted termite workers as food in the laboratory. Interestingly, this individual was found dead within the fungus garden of an Atta sexdens artificial nest in the same lab, so we can not rule out the possibility that B. scambognathus lives inside Atta nests (or another fungus grower ant), which could explain the difficulty to find this species in nature, and in part its status of rarity.

The second worker collected up to now was recovered alive along with other ants, several different terrestrial arthropods, and soil particles from a leaf litter sample. Once in a plastic recipient, the worker feigned death upon disturbance, in typical Basiceros style, remaining so for several minutes, and reassuming movement quite slowly. Also as expected for a basicerotine ant, the body of the worker was tightly covered by a layer of dried soil ( Hölldobler & Wilson, 1986). From the same sample we recovered also several workers of an unidentified Apterostigma and many Blepharidatta conops workers.

Examined material: no locality, no date (no collector), [Gift from B. Bolton ( BMNH) #59 74] (1 Gyne) ( ANIC) . BRASIL: Amapá: Amaparí , 8‑10.xi.1993 (W. França), [Tucano‑2] (1 Male) ( INPA); (F.F. Ramos) (1 Male) ( INPA); (N. Bittencourt) (1 Male) ( INPA) ; 9‑10.xi.1993 (A. Pena) (1 Male) ( INPA) ; 10‑14.xi.1993 (F.F. Ramos) (1 Male) ( INPA) . Amazonas: Estirão do Equador, Rio Javari , ix.1979 (Alvarenga) (1 Gyne, 1 Male) ( MZSP) ; N of Manaus, Reserva Ducke , 22‑26.xi.1966 (no collector), [Malaise trap] (3 Males) ( MZSP) ; 14.viii.1981 (C.B. Fairchild & J.A. Rafael), [Malaise] (1 Male) ( INPA) ; 28.ix.1981 (J.A. Rafael), [Malaise] (1 Male) ( INPA) . Bahia: Maracás, Fazenda Maria Inácia , 24‑29.xi.1990 (Brandão; Diniz & Oliveira) (1 Male) ( MZSP) . Goiás: Serra da Mesa, Colinas do Sul (14°01’S 48°12’W), 2‑15.xii.1995 (Silvestre; Dietz & Campaner), [Cerrado] (1 Male) ( MZSP) ; Jataí , xii.1972 (F.M. Oliveira), [#8911] (1 Gyne) ( MZSP) . Maranhão: Estreito, Fazenda Itaueras (6°31’54”S 47°22’16”W), 12‑22.vi.2006 (R.R. Silva & R.M. Feitosa) (1 Worker) ( MZSP) . Mato Grosso: Sinop (12°31’S 55°37’W), x.1974 (M. Alvarenga), [#12306] (1 Gyne) ( MZSP) ; [#12307] (6 Males) ( MZSP); (Alvarenga & Roppa) , [#12517] (1 Male) ( MZSP) ; [#12551] (1 Gyne) ( MZSP) ; [#12552] (4 Males) ( MZSP) ; Vila Vera , x.1973 (M. Alvarenga), [#10253] (6 Males) ( MZSP) . Pará: Santarém Novo, Fazenda Jaburu , 7‑9. i.1993 (J. Dias) (1 Male) ( INPA) ; Igarapé‑Açú , i.1949 (Gonçalves) (1 Gyne) ( MCZC) . Rondônia: 62 km S of Ariquemes, Fazenda Rancho Grande (10°32’S 62°48’W), 12‑22.xi.1991 (E.M. Fisher) (3 Males) ( PWRD) . Roraima: Ilha de Maracá, Rio Uraricoera , 18‑28.viii.1987 (J.A. Rafael et al.) (1 Male) ( INPA) .

Figures

FIGURE 1: Basiceros scambognathus, worker; a) head in full‑face view; b) body in profile.

FIGURE 2: B. scambognathus, gyne; a) head in full‑face view; b) body in profile; c) detail of the mandibular groove in full frontal view.

FIGURE 3: Basiceros scambognathus, male; a) head in full‑face view; b) body in profile.

FIGURE 4: Distribution map of Basiceros scambognathus.