Basiceros scambognathus

Basiceros scambognathus
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Hymenoptera
Family:	Formicidae
Subfamily:	Myrmicinae
Tribe:	Attini
Genus:	Basiceros
Species:	B. scambognathus
Binomial name
	Basiceros scambognathus; (Brown, 1949) Specimen labels

Basiceros scambognathus is one of the most obscure taxa in terms of natural history.

Identification

Probst & Brandão (2022) - Mandibles bizarre, subtriangular, apical portion strongly curved ventrally, oblique basidorsal sulcus present. Clypeus and head dorsa densely covered with decumbent squamiform hairs. Anapleural sulcus present, mesoanepisternum depressed.

Considering the known Basiceros males, the males of B. scambognathus have unique mandibular morphology, with the apical tooth narrow and projected, isolated from the other teeth on the masticatory margin; this tooth can vary in size, width, and be variably close to the subapical tooth. Additionally, they present the maximum degree of antennal torsion among all knownBasiceros.

Keys including this Species

Key to Basiceros species

Distribution

Souza & Delabie’s (2013) produced a geographic distribution model for B. scambognathus.

Latitudinal Distribution Pattern

Latitudinal Range: 0.833333333° to -17.881°.


North Temperate	North Subtropical	Tropical	South Subtropical	South Temperate

Source: AntMaps

Distribution based on Regional Taxon Lists

Neotropical Region: Brazil (type locality), Venezuela.

Distribution based on AntMaps

Distribution based on AntWeb specimens

Check data from AntWeb

Countries Occupied

Number of countries occupied by this species based on AntWiki Regional Taxon Lists. In general, fewer countries occupied indicates a narrower range, while more countries indicates a more widespread species.

Estimated Abundance

Relative abundance based on number of AntMaps records per species (this species within the purple bar). Fewer records (to the left) indicates a less abundant/encountered species while more records (to the right) indicates more abundant/encountered species.

Biology

Probst & Brandão (2022) - The aberrant mandibles of B. scambognathus likely reflect specific predatory behavior. Feitosa et al. (2007) mention that the first dealate gyne was collected in Uruaçu, State of Goiás, Brazil in 1995 (by CRFB) and kept in artificial conditions for a few weeks, with the only behavioral record mentioning the gyne having accepted termites as food. Unfortunately, most records for this species are of males or alate gynes, usually collected with flight-intercept traps, thus preventing inferences about nesting and foraging behaviors and potential interactions with other species.

Although workers recorded so far have been found in litter samples, it is important to mention that the laboratory- maintained gyne escaped its terrarium and was eventually found dead inside the fungus garden of an artificial leaf-cutter nest of Atta sexdens in the same laboratory. Feitosa et al. (2007) conjecture the possibility of B. scambognathus nesting inside Atta (or another fungus-growing ant) nests, partially explaining the difficulty of finding this species in nature.

Castes

Queen

Probst & Brandão 2022. Figure 22. Basiceros scambognathus, gyne (MZSP, Brazil: Minas Gerais); A. full-face view, B. dorsal view, C. lateral view. Scale bars: A = 0.5 mm, B–C =1 mm.

Images from AntWeb


Queen (alate/dealate). Specimen code casent0172825. Photographer April Nobile, uploaded by California Academy of Sciences.	Owned by MCZ, Cambridge, MA, USA.


Queen (alate/dealate). Specimen code casent0172317. Photographer April Nobile, uploaded by California Academy of Sciences.	Owned by ANIC, Canberra, Australia.

Male

Probst & Brandão 2022. Figure 22. Basiceros scambognathus, male (CASENT0914889, Brazil: Rondônia; images by Michele Esposito [CAS], edited); D. full-face view, E. dorsal view, F. lateral view. Scale bars: D = 0.2 mm, E–F = 0.5 mm.

Phylogeny

Basiceros

	Basiceros sp.n.A

	Basiceros convexiceps

	Basiceros manni

	Basiceros singularis

Basiceros scambognathus

Basiceros conjugans

	Basiceros disciger

	Basiceros militaris

Based on Probst et al., 2019.

Nomenclature

The following information is derived from Barry Bolton's Online Catalogue of the Ants of the World.

scambognathus. Creightonidris scambognatha Brown, 1949f: 89 (q.) BRAZIL (Goiás).
- Type-material: holotype queen.
- Type-locality: Brazil: Goiás, Campinas, x.1935 (Schwarzmeier).
- Type-depository: MZSP.
- Feitosa, et al. 2007: 19 (w.m.).
- Combination in Basiceros: Fernández, 2003d: 392.
- Status as species: Brown & Kempf, 1960: 178; Kempf, 1972a: 81; Bolton, 1995b: 146; Fernández, 2003d: 392; Feitosa, et al. 2007: 19 (redescription); Bezděčková, et al. 2015: 115; Fernández & Serna, 2019: 844; Probst & Brandão, 2022: 51 (redescription).
- Distribution: Brazil, Colombia, French Guiana, Peru, Venezuela.

Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.

Description

Worker

Worker: Size relatively medium (TL between 4,9 and 8,7 mm). Reddish to dark‑brown in color. Integument thick and in general densely sculptured; foveolate over head disc, mesosoma with conspicuous deep to shallowly set punctuation, densely punctate over most or all the gaster. Pilosity conspicuous and bizarre; sub‑decumbent hairs abundant, spatulate, squamiform or plumose; erect abundant or sparse hairsclavate or stout and truncate. Labrum with fine sensorial hairs. Head trapezoidal, triangular or rounded posteriorly; posterior and lateral head borders always visible and clearly distinct, and either rounded or crested, or else combined into curving, continuous or near continuous crest around posterior margin of head. Dorsal surface of head flattened to depressed, slightly convex in some species. Mandibles sub‑porrect, triangular to subtriangular, with straight, opposable, multidenticulate masticatory borders; apical portion from straight to strongly bent ventrally; basal portion flat and smooth to moderately convex and sculptured in frontal view; blade narrowed near insertion, the resulting peduncle either partly exposed or entirely hidden beneath clypeus, interspace between basal mandibular margin and anterior clypeal border present to absent in varying degrees. Eyes relatively well developed (ocular index ca 11). Antennal scape flattened, broad, and lobate at the basal portion; funiculus moderately clavate with 11 segments.

Mesosoma usually robust. Metanotal groove present. Propodeal teeth always triangular in lateral view, lamelliform, short, more or less acute, and connected to each other by a transverse carina. Petiole pedunculate and usually with ventral carina bearing one or more teeth. Gastric dorsum with a median longitudinal strip slightly impressed or devoid of pilosity. According to Brown (1974) Basiceros has 5 Malpighian tubules.

All of the remainder of the nomenclature section is from Probst & Brandão (2022)

(n=2): HL 1.37–1.39, HL2 1.37–1.40, HW1 1.12–1.15, MdL 0.59–0.65, SL1 0.84–0.87, SL2 1.03–1.05, PDL 0.11–0.12, A3L 0.03, AFL 0.36–0.40, FuL 0.97–1.00, EL 0.08–0.13, EW 0.06–0.09, ML 1.62, MfL 1.23–1.27, MtL 1.03–1.05, PH 0.33–0.40, PL 0.72–0.75, PW 0.28–0.34, PPL 0.50–0.56, PPW 0.50–0.59, GL 1.80–1.93, GW 1.00–1.21, TL 6.65–6.87, CI 801–84, CS 1.25–1.26, MCI 42–47, SI 89–93, ESI 7.46–12.12, SAI2 257–287, EI1 0.11–0.17, MFI 88–93, PTI 177–228.

Medium size comparatively. Coloration reddish-brown to dark brown; appendages lighter, chocolate to brown. Mandibles generally lighter than predominant body coloration; dorsa covered by obsolete and sparse piligerous punctuation; basal portion with clavate pilosity suberect to subdecumbent; mandibular apex with medium yellowish setae. Basimandibular seta present, narrow and erect. Clavate suberect hair 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 same morphology as clypeal pilosity, slightly more sparse; erect and lightly clavate pilosity as follows: a pair of isolated hairs on the posterior region of frons, close to the median sulcus of vertexal margin; a pair of hairs present or not in front of eyes, a pair near the posterior limit of eyes; six pairs on vertexal corners and eight pairs starting from the superficial emargination projected above the eyes until the vertexal margin. Mesosoma, petiole, postpetiole, and first gastral sternite with basal pilosity short, appressed to decumbent, formed by squamiform hairs. Erect to suberect pilosity on mesosomal dorsum, posterolateral portion of pronotum and gastral segments II–VII relatively abundant, clavate, from whitish to yellowish; pygidium with short, filiform, suberect hairs. A pair of clavate hairs on the anteroventral margin of the postpetiolar sternite. Antennal scapes with whitish to yellowish decumbent pilosity, squamiform; funiculus covered by short, appressed, and yellowish setae. Legs with decumbent and yellowish pilosity, squamiform, becoming thinner towards the tarsus.

Surface of antennal scrobes rugo-punctuate; head dorsum with irregular rugae forming fovea of different sizes, internally punctuate. Pronotum strongly punctuate-reticulate on the lateral portion; anterior portion rugose, punctuate between rugulae spaces. Surface of meso- and metapleura, petiolar node, postpetiole, and gaster slightly shiny and abundantly punctuate-reticulate. Procoxae punctuate-foveate.

Head oblong; posterolateral corners round; vertexal margin concave medially. Vertexal crest present as a ca rina-shaped lateral lift, close to the beginning of lateral convexity of head. Mandibles aberrant and subtriangular; external margin of basal portion subparallel; masticatory margin straight bearing 14–16 teeth, apical tooth slightly broader and longer; apical portion of mandibles strongly curved ventrally to the midpoint of their length; basal angle acute; basal portion of mandibles slightly convex in lateral view; in full-face view, oblique sulcus present on basal portion, extending from the masticatory margin to at least half of the lamina; with mandibles closed, these opposing sulci converge, with the aspect of a circumflex accent, posteriorly directed. Frontoclypeal surface convex; anterior margin concave. Tumosity present in the central portion of the head dorsum, circular-shaped and with deep concavity, giving it a ring-like appearance. 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 strongly crenulated. Antennal apical segment longer than the sum of four anterior antennomeres.

Mesosoma robust; in lateral view, promesonotal profile slightly convex dorsally; metanotal suture strongly impressed, extending as the anapleural sulcus, transversely rugose-costulate. Mesopleura flange transversely scrobiculate, sculpture short; flange reaching a deep and digitiform epicnemial fossa. Propodeum posteriorly oblique; propodeal projections short, triangular and slightly upwards, connected by strong transverse carina; propodeal spiracle round, spiracle relatively projected laterally side and directed posteriorly. Petiole nodiform, peduncle short and shorter than the petiolar node; node prominent and bulging, curved caudad. Subpetiolar process consisting of series of sharp denticles. In lateral view, postpetiole slightly longer than length of petiolar node; slightly 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; postpetiole subtrapezoidal, as long as wide, lateral margins diverging posteriorly and narrowed so that gaster is widely connected to postpetiole. Gaster oval; anterior margin concave; first gastral sternite visibly longer than tergite. Metabasitarsus conspicuously long, longer than metatibia. Tarsal claws simple.

Queen

(n=3). HL 1.34; HL2 1.45–1.47, HW 1.28, MdL 0.66–0.69, SL1 0.91–0.94, SL2 1.09–1.13, PDL 0.13, A3L 0.03, AFL 0.38, FuL 1.03–1.06, EL 0.28, EW 0.25–0.27, LOD 0.08–0.09, MOD 0.08, OOD 0.38–0.39, ML 1.94–2.03, MSL 0.94–1.06, MSW 1.00–1.06, MLL 0.34–0.38, MLW 0.50–0.59, MfL 1.31–1.38, MtL 1.06–1.13, PH 0.47–0.50, PL 0.84, PW 0.38–0.41, PPL 0.59–0.63, PPW 0.61–0.69, GL 2.63–2.66, GW 1.50–1.53, TL 8.06–8.13, CI 95, CS 1.31, MCI 48–51, SI 85–87, ESI 25–25, SAI2 280–300, EI1 0.40–0.42, MTI 100–106, MLI 145–158, FI 93–97, PTI 168–180. (In bold: gaster dilated on all measured gynes; measurement was corrected by subtracting pleura range from measured value).

Coloration similar or slightly darker than conspecific worker; slightly larger size; mesosomal sculpture more developed. Ocelli present; median ocellus inserted at the posterior limit of the circular concavity on frons; median ocelli inserted close to the median vertexal sulcus. Head pilosity as on conspecific workers; more abundant on frons. Mesosomal pilosity as follows: basal pilosity on pronotum as in the workers and present in the same way, only slightly sparser on mesoscutum and mesoscutellum dorsa; erect and clavate hairs present in the following configuration: two clavate hairs on the central portion of pronotum; 20–22 hairs arranged on the dorsum of mesoscutum; two hairs on each parascutal flange; 4–6 hairs on mesoscutellum dorsum, 2–4 hairs on metanotum. Other pilosity as presented in the conspecific workers. Sculpture very similar to conspecific workers, only stronger marked on some portions, such as the petiole and postpetiole. Mesoanepisternum, meso- and metakatepisternum with smooth and shiny or matt portion, variably (sometimes only part of mesoanepisternum, only the posterolateral corner of the mesokatepisternum or the entire portion of metakatepisternum; never all these portions are smooth and shiny or matt at the same time. Forewing type 2; hindwing with five submedian hamuli.

Male

(n=2). HL 0.94–1.12, HW1 0.90–1.00, HW2 1.13–1.19, MdL 0.42–0.47, SL2 0.25–0.28, PDL 0.09–0.12, A3L 0.34–0.37, AFL 0.59–0.65, EL 0.38–0.41, EW 0.34–0.37, LOD 0.09, MOD 0.09, OOD 0.34, ML 1.67–1.90, MSL 0.92–1.03, MSW 0.86–1.09, MLL 0.28–0.31, MLW 0.50–0.59, MfL 1.25–1.38, MtL 0.97–1.00, PH 0.31–0.36, PL 0.69–0.78, PW 0.31–0.36, PPL 0.43–0.48, PPW 0.53, GL 1.50–1.59, GW 1.15–1.31, TL 5.65–6.35, CI 88–96, CS 0.92–1.06, MCI 41–45.00, SI 25–31, ESI 133–162, SAI 66–81, SAI2 38–47, EI1 0.73–0.78, EI2 80–84, MTI 93–106, MLI 177–190, MFI 72–72, PTI 217–220.

Coloration dark brown, with areas slightly ferruginous (e.g., propodeal lobes, lateral of postpetiole, and first gastral tergite and sternite). Appendages yellowish to light brown. Pilosity primarily composed of long filiform whitish hairs densely covering the body, mainly head, dorsum of promesonotum, and gaster.

Body sculpture mainly punctuate-rugose, exception to the mesoanepisternum and metakatepisternum, with portions that are variably smooth and shiny or subopaque; head covered with irregular rugae; mesosoma with irregular rugae on dorsal surface of promesonotum, in the lower portion of the mesopleuron, lateral of propodeum and petiolar peduncle; other integument covered by coarse reticulate punctuations, mainly on the lateral surfaces of the mesosoma, petiole and postpetiole. Gaster densely punctuate-reticulate, punctuations fine.

Mandibles subtriangular, as long as wide. Masticatory margin with 10 conical teeth, third and fourth teeth from the base slightly broader than others; apical tooth acute, conspicuously separated from the subapical and projected; external margins of mandibles strongly convex on the basal portion and apically straight, apex almost concave. Head ovoid. Ocelli large and positioned on cephalic crest close to occipital margin; median ocellus inserted before a transversely rugose cleft; lateral ocelli with interocellar rugae. As for other Basiceros males, a deep concave sulcus is present along the frontoclypeal region. Central disc of clypeus convex, central portion raised forming a distinct circular area; anterior margin and lateral portions slightly depressed. Anterior clypeal margin smooth and slightly concave. Eyes globular, large. Antennal fossa shallow. In dorsal view, mesoscutum slightly cuneiform anteriorly, as wide as long; anterior margin with smooth and shiny median carina, extending along dorsum of mesoscutum to the point of convergence of 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 sulcus. Propodeal projections round, propodeal lobes auricular and slightly narrow. Petiole and gaster as in conspecific females. Subpetiolar projection consisting of only a small triangular lamella, inserted just before the beginning of node, or by this lamella followed by 1–2 denticles; petiolar spiracle projected laterally. Forewing type 2; hindwing with five submedian hamuli.

Type Material

BRAZIL: Goiás: Campinas (current West Zone of Goiânia), x.1935, Schwarzmaier col. (one gyne— holotype) (examined).

Etymology

From Greek, skambos, curved, arched + gnathos, mandible. Dr. William Brown Jr. must have named this species based on the aberrant shape of its mandibles, whose apical region is conspicuously facing the ventral region.

Determination Clarifications

Brown (1949: 91) discusses the locality of the gyne erroneously associated to B. singularis, in the passage reproduced below: “It was noted above that I consider this to be the same form Frederik Smith described 89 years ago as the female of Ceratobasis singularis, the only doubt stemming from certain differences in Smith’s figures, which are often inaccurate and vague. I do not know whether Ega [currently Tefé] is the proper locality for Smith’s specimen, but seemingly it was taken somewhere in the Amazon Basin by the famous naturalist Henry Bates. Although Smith cautioned Bates, as he says, to keep good records and proper associations of the castes of one species, it appeared that Smith himself had a perverse genius for mixing up these same records and associations as few have ever done. Most of Smith’s locality records bear little examination, and it is not safe to accept them too specifically for types. Many previous authors have flayed the same hide while themselves committing errors as grievous, so it is perhaps best to let Mr. Smith rest in peace while his detractors have their well-deserved turn.”

However, later collections show that perhaps Smith was not mistaken. Basiceros scambognathus has a wide geographic distribution and there are scattered records in the Brazilian territory, from Minas Gerais to the Central and Northern States, in addition to French Guiana, Peru, and Venezuela. This species probably occurs in Suriname. New records for the present study are represented mainly by males collected in Malaise traps. Feitosa et al. (2007) mentions that the apparent discontinuity of distribution—in the form of scattered records—may reflect the use of inappropriate techniques for collecting this taxon, as aspects of its natural history are entirely unknown. This taxon was probably collected in southern Colombia (Dr. Benoit Guénard, University of Hong Kong, pers. comm.), but it was impossible to examine such material in the present work, so that record is not confirmed.

References

References based on Global Ant Biodiversity Informatics

Brown W. L., Jr. 1949. Revision of the ant tribe Dacetini: IV. Some genera properly excluded from the Dacetini, with the establishment of the Basicerotini new tribe. Trans. Am. Entomol. Soc. 75: 83-96.
Castilho A. C. C., J. H. C. Delabie, M. I. Marques, J. Adis, and L. F. Mendes. 2007. New Records of the Cryptobiotic ant Creightonidris scambognatha Brown (Hymenoptera: Formicidae) from Brazil. Neotropical Entomology 36(1):150-152.
Feitosa, R.M., C.R.F. Brandao and B.H. Dietz. 2007. Basiceros scambognathus (Brown, 1949) n. comb., with the first worker and male descriptions, and a revised generic diagnosis (Hymenoptera: Formicidae: Myrmicinae). Papeis Avulsos de Zoologia 47(2):31-42
Franco W., N. Ladino, J. H. C. Delabie, A. Dejean, J. Orivel, M. Fichaux, S. Groc, M. Leponce, and R. M. Feitosa. 2019. First checklist of the ants (Hymenoptera: Formicidae) of French Guiana. Zootaxa 4674(5): 509-543.
Pires de Prado L., R. M. Feitosa, S. Pinzon Triana, J. A. Munoz Gutierrez, G. X. Rousseau, R. Alves Silva, G. M. Siqueira, C. L. Caldas dos Santos, F. Veras Silva, T. Sanches Ranzani da Silva, A. Casadei-Ferreira, R. Rosa da Silva, and J. Andrade-Silva. 2019. An overview of the ant fauna (Hymenoptera: Formicidae) of the state of Maranhao, Brazil. Pap. Avulsos Zool. 59: e20195938.
Probst R. S., B. D. Wray, C. S. Moreau, and C. R. F. Brandao. 2019. A phylogenetic analysis of the dirt ants, Basiceros (Formicidae: Myrmicinae): inferring life histories through morphological convergence. Insect Systematics and Diversity 3(4): 1–12.
Probst da Silva R. 2015. Revisao taxonomica e analise filogenetica de Basiceros Schulz, 1906 (Formicidae, Myrmicinae, Basicerotini). Master Thesis Museu de Zoologia da Universidade de Sao Paulo. 263 pages.