Basiceros

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Basiceros
Basiceros manni
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Attini
Genus: Basiceros
Schulz, W.A., 1906
Type species
Meranoplus singularis, now Basiceros singularis
Diversity
9 species
(Species Checklist, Species by Country)

Basiceros manni casent0052769 profile 1.jpg

Basiceros manni

Basiceros manni casent0052769 dorsal 1.jpg

Specimen Label

Synonyms

Known only from Neotropical rainforests, the elusiveness of Basiceros is reinforced by an impressive form of crypsis exhibited by adult workers and queens, which accumulate soil and leaf litter particles on their integument with the aid of specialized setae. Little information is available regarding their natural history. Currently a member of the ‘Basiceros-genus group’ (Eurhopalothrix, Octostruma, Protalaridris, Rhopalothrix, Talaridris). For mouthparts, labral and mandibular morphologies present considerable variation in the Basiceros-genus group, likely a result of adaptive evolution. In Basiceros, those differences can be observed in the labrum shape and the various degrees of development of the labral cleft and the clypeomandibular space. Mouthpart traits indicate a strong correlated evolutionary history potentially associated with specialized feeding habits (Probst et al. 2019).

Identification

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Keys including this Genus

 

Keys to Species in this Genus

Distribution

Probst & Brandão (2022) - Neotropical. The northernmost record comes from Honduras for B. manni, the southernmost record from the State of Rio Grande do Sul, Brazil, for B. disciger. In terms of elevation, Basiceros might peak its abundance at low and medium elevation. This is supported by the absence of specimens in collections from high-elevation forests (>1500m) and from studies focusing on ant diversity along altitudinal gradients (e.g., Scott-Santos 2008).

Distribution and Richness based on AntMaps

Species by Region

Number of species within biogeographic regions, along with the total number of species for each region.

Afrotropical Region Australasian Region Indo-Australian Region Malagasy Region Nearctic Region Neotropical Region Oriental Region Palaearctic Region
Species 0 0 0 0 0 9 0 0
Total Species 2841 1736 3045 932 835 4379 1741 2862

Biology

Probst et al. (2019) - Direct evidence of Basiceros preying on gastropods comes from photographic accounts - a larva of Basiceros singularis feeding on a gastropod with a rounded shell. For other Basiceros species, data on feeding preference are scarce. Part of a colony of Basiceros conjugans was collected in Peru, nesting in a rotten log, and the trash chamber included a gastropod shell, ant remains, and a cephalic capsule of Isoptera (Syntermitinae) (Probst 2015), suggesting that B. conjugans could have scavenger habits.

Mandible shape is known to be a highly labile trait in ants; however, the labrum is often overlooked in the discussions of mouthpart evolution. This work provides the first step for examining ecological specialization of members of the Basiceros-genus group in the light of mouthpart traits, showing transitions in the mandible and labrum, probably due to prey specialization.

Probst & Brandão (2022) - Scarce information about the natural history of Basiceros from the literature (Weber 1950, Brown 1974, Hölldobler & Wilson, 1986) mentions the dirt ants as being cryptic, with slow-moving habits, and presenting thanatosis when disturbed. Apparently, no recruitment has been recorded, and workers forage solitarily. As far as it is known, Basiceros do not excavate nests, and their colonies are usually found in leaf litter interstices, occupying soil cavities, hollow or rotten logs, seedpods, or preferably in areas with superficial root system or close to the base of large trees. Little is known about its colonial structure (nests usually have ~50–100 individuals); collection records suggested that some species may be polygynic. Intercastes are reported for the first time in the present study. The unique morphology and the usually dense layer of soil and litter particles covering the integument of some species suggest that the dirt ants have a dietary preference—situation reinforced by an impressive morphological variation on the mouthparts across the genus (Probst et al. 2019).

Life History Traits

  • Mean colony size: 9-32; 50–100 (Greer et al., 2021; Probst & Brandão 2022)
  • Compound colony type: not parasitic (Greer et al., 2021)
  • Nest site: hypogaeic (Greer et al., 2021)
  • Diet class: predator (Greer et al., 2021)
  • Foraging stratum: subterranean/leaf litter (Greer et al., 2021)
  • Foraging behaviour: solitary (Greer et al., 2021)

Castes

Intercaste

Probst & Brandão (2022) - As mentioned for Basiceros disciger and Basiceros militaris, Basiceros singularis displays intercastes. The examined morphological mosaic for this species has gynes virtually identical to conspecific workers, differing only by the presence of a median and/or lateral ocelli and a slight scutellar impression, and the most aberrant case of ergatoidism within the genus, in which a gyne presented alar rudiments, even without showing complete development of the mesosomal sclerites associated with flight. Obviously, this brachypterous gyne could not fly. Similar to B. militaris, intercastes and true gynes co-occur in the same colony. Together with a general morphology analogous to conspecific workers, it reinforces a scenario similar to that found by Molet et al. (2009) for Mystrium gynes in Madagascar, with ergatoids having functional ovaries, spermatheca, and alar rudiments, acting as a “multitasking” caste within the colony. Almost all specimens of B. singularis are collected covered by a thick layer of particles that prevents the visualization of morphological changes on the mesosoma and head. The intercaste mosaicism was revealed after the cleaning of several specimens; therefore, the presence of intercastes in this species is probably underestimated.

Male

Probst & Brandão 2022. Figure 1. Wing venation of Basiceros males. A. forewing and B. hindwing of B. conjugans (RSPPC, Peru). C. forewing of B. manni male (MCZ, Costa Rica: Heredia). Fused veins are indicated with a plus sign and crossveins by a dash. Cell names (in white) are indicated in italics. Scale bars: 1 mm.

Morphology

Worker Morphology

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• Antennal segment count: 12 • Antennal club: 2 • Palp formula: 2,2; 1,2 • Total dental count: 11-15 • Spur formula: 0,0 • Eyes: 11-100 ommatidia • Pronotal Spines: absent • Mesonotal Spines: absent • Propodeal Spines: dentiform • Petiolar Spines: absent • Caste: none or weak • Sting: present • Metaplural Gland: present • Cocoon: absent


Karyotype

All Karyotype Records for Genus

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Taxon Haploid Diploid Karyotype Locality Source Notes
Basiceros convexiceps 20 20M Brazil Mariano et al., 2013

Phylogeny

Myrmicinae
Myrmicini
Pogonomyrmecini
Stenammini
Solenopsidini
Attini

Ochetomyrmex  (2 species, 0 fossil species)

Tranopelta  (2 species, 0 fossil species)

Diaphoromyrma  (1 species, 0 fossil species)

Lachnomyrmex  (16 species, 0 fossil species)

Blepharidatta  (4 species, 0 fossil species)

Allomerus  (8 species, 0 fossil species)

Wasmannia  (11 species, 0 fossil species)

Pheidole  (1,294 species, 7 fossil species)

Cephalotes  (123 species, 16 fossil species)

Procryptocerus  (44 species, 0 fossil species)

Strumigenys  (879 species, 4 fossil species)

Phalacromyrmex  (1 species, 0 fossil species)

Pilotrochus  (1 species, 0 fossil species)

Protalaridris  (7 species, 0 fossil species)

Rhopalothrix  (19 species, 0 fossil species)

Basiceros  (9 species, 0 fossil species)

Octostruma  (35 species, 0 fossil species)

Eurhopalothrix  (54 species, 0 fossil species)

Talaridris  (1 species, 0 fossil species)

Acanthognathus  (7 species, 1 fossil species)

Daceton  (2 species, 0 fossil species)

Lenomyrmex  (7 species, 0 fossil species)

Microdaceton  (4 species, 0 fossil species)

Orectognathus  (29 species, 0 fossil species)

Colobostruma  (16 species, 0 fossil species)

Epopostruma  (20 species, 0 fossil species)

Mesostruma  (9 species, 0 fossil species)

Paleoattina

Apterostigma  (44 species, 2 fossil species)

Mycocepurus  (6 species, 0 fossil species)

Myrmicocrypta  (31 species, 0 fossil species)

Neoattina

Cyatta  (1 species, 0 fossil species)

Kalathomyrmex  (1 species, 0 fossil species)

Mycetarotes  (4 species, 0 fossil species)

Mycetosoritis  (2 species, 0 fossil species)

some Cyphomyrmex  (23 species, 2 fossil species)

some Cyphomyrmex

Paramycetophylax  (1 species, 0 fossil species)

Mycetophylax  (21 species, 0 fossil species)

Mycetagroicus  (4 species, 0 fossil species)

Mycetomoellerius  (31 species, 1 fossil species)

Sericomyrmex  (11 species, 0 fossil species)

Xerolitor  (1 species, 0 fossil species)

Paratrachymyrmex  (9 species, 0 fossil species)

Trachymyrmex  (9 species, 0 fossil species)

Amoimyrmex  (3 species, 0 fossil species)

Atta  (20 species, 1 fossil species)

some Acromyrmex  (56 species, 0 fossil species)

some Acromyrmex

Pseudoatta  (2 species, 0 fossil species)

Crematogastrini

Rostromyrmex  (1 species, 6 fossil species)

Cardiocondyla  (90 species, 0 fossil species)

Ocymyrmex  (34 species, 0 fossil species)

Nesomyrmex  (84 species, 2 fossil species)

Xenomyrmex  (5 species, 0 fossil species)

Terataner  (14 species, 0 fossil species)

Atopomyrmex  (3 species, 0 fossil species)

Cataulacus  (65 species, 3 fossil species)

Carebara  (249 species, 9 fossil species)

Diplomorium  (1 species, 0 fossil species)

Melissotarsus  (4 species, 1 fossil species)

Rhopalomastix  (14 species, 0 fossil species)

Calyptomyrmex  (38 species, 0 fossil species)

Strongylognathus  (27 species, 0 fossil species), Tetramorium  (598 species, 2 fossil species)

Cyphoidris  (4 species, 0 fossil species)

Dicroaspis  (2 species, 0 fossil species)

Aretidris  (2 species, 0 fossil species)

Vollenhovia  (83 species, 3 fossil species)

Dacetinops  (7 species, 0 fossil species)

Indomyrma  (2 species, 0 fossil species)

Crematogaster  (783 species, 3 fossil species)

Meranoplus  (91 species, 0 fossil species)

Lophomyrmex  (13 species, 0 fossil species)

Adlerzia  (1 species, 0 fossil species)

Recurvidris  (12 species, 0 fossil species)

Stereomyrmex  (3 species, 0 fossil species)

Trichomyrmex  (29 species, 0 fossil species)

Eutetramorium  (3 species, 0 fossil species)

Royidris  (15 species, 0 fossil species)

Malagidris  (6 species, 0 fossil species)

Vitsika  (16 species, 0 fossil species)

Huberia  (2 species, 0 fossil species)

Podomyrma  (62 species, 1 fossil species)

Liomyrmex  (1 species, 0 fossil species)

Metapone  (31 species, 0 fossil species)

Kartidris  (6 species, 0 fossil species)

Mayriella  (9 species, 0 fossil species)

Tetheamyrma  (2 species, 0 fossil species)

Dacatria  (1 species, 0 fossil species)

Proatta  (1 species, 0 fossil species)

Dilobocondyla  (22 species, 0 fossil species)

Secostruma  (1 species, 0 fossil species)

Acanthomyrmex  (19 species, 0 fossil species)

Myrmecina  (106 species, 0 fossil species)

Perissomyrmex  (6 species, 0 fossil species)

Pristomyrmex  (61 species, 3 fossil species)

some Lordomyrma  (36 species, 0 fossil species)

Propodilobus  (1 species, 0 fossil species)

Lasiomyrma  (4 species, 0 fossil species)

some Lordomyrma

Ancyridris  (2 species, 0 fossil species)

some Lordomyrma

Paratopula  (12 species, 0 fossil species)

Poecilomyrma  (2 species, 0 fossil species)

Romblonella  (10 species, 0 fossil species)

Rotastruma  (3 species, 0 fossil species)

Gauromyrmex  (3 species, 0 fossil species)

Vombisidris  (19 species, 0 fossil species)

Temnothorax  (512 species, 7 fossil species)

Harpagoxenus  (4 species, 0 fossil species)

Formicoxenus  (8 species, 0 fossil species)

Leptothorax  (20 species, 0 fossil species)

See Phylogeny of Myrmicinae for details.

Nomenclature

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

  • BASICEROS [Myrmicinae: Basicerotini]
    • Basiceros Schulz, W.A. 1906: 156. Replacement name for Ceratobasis Smith, F. 1860c: 78. [Junior homonym of Ceratobasis Lacordaire, 1848: 362 (Coleoptera).]
    • Basiceros senior synonym of Aspididris: Brown, 1974c: 132.
    • Basiceros senior synonym of Creightonidris: Fernández, 2003d: 314, 392; Feitosa, Brandão & Dietz, 2007: 17.
    • Basiceros senior synonym of Acanthidris, Eurhopalothrix, Heptastruma, Octostruma, Protalaridris, Rhopalothrix, Talaridris: Baroni Urbani & De Andrade, 2007: 88.
  • ASPIDIDRIS [junior synonym of Basiceros]
    • Aspididris Weber, 1950c: 3. Type-species: Aspididris militaris, by monotypy.
    • Aspididris junior synonym of Basiceros: Brown, 1974c: 132.
  • CERATOBASIS [junior homonym, see Basiceros]
    • Ceratobasis Smith, F. 1860c: 78. Type-species: Meranoplus singularis, by monotypy. [Junior homonym of Ceratobasis Lacordaire, 1848: 362 (Coleoptera).]
    • Basiceros Schulz, W.A. 1906: 156, replacement name for Ceratobasis Smith.
  • CREIGHTONIDRIS [junior synonym of Basiceros]
    • Creightonidris Brown, 1949f: 89. Type-species: Creightonidris scambognatha, by original designation.
    • Creightonidris junior synonym of Basiceros: Fernández, 2003d: 314, 392; Feitosa, Brandão & Dietz, 2007: 17.


Probst & Brandão (2022) - The workers and gynes of Basiceros are differentiated from the other members of the Basiceros-genus group by the combination of body size (the largest within this group), antennae with 12 segments, presence of hairs on the postpetiolar sternite, basimandibular seta, and body pilosity (usually composed of a double layer of specialized hairs). Males can be distinguished by the combination of the twisted antennae, mandible shape, petiole and postpetiole shape in dorsal view, pattern of wing venation, and mesopleuron sculpture. The most important morphological characters to distinguish between workers/gynes of different Basiceros species are the head and labrum shapes, mesosoma profile in lateral view, and the pattern of specialized pilosity. For males, head and mandible shape, mesosoma in anterior view, shape of petiolar node in lateral view, and mesopleuron sculpture are important.

Caste diagnosis

Worker Comparatively medium-sized ants (TL: 4.5 to 8.7 mm). Color amber-yellow to black. Integument thick, usually densely sculptured: punctuate/foveate (or a combination of both) or rugose. Pilosity conspicuous and generally specialized; erect setae from sparse to abundant, usually clavate; subdecumbent pilosity sparse to abundant, squamiform, spatulate-clavate or plumose. Labrum shape variable, either long and cuneiform and bilobed apically or somewhat lunate with a rounded distal margin, labral surfaces with specialized setae (probably with sensorial role) along its distal margin and sometimes in the ventral margin. Head trapezoidal, oblong or posteriorly disc-shaped; lateral and vertexal margins distinctly visible: rounded, angulate or as a continuously or medially emarginated crest along the posterior margin. Mandibles triangular or subtriangular, usually elongated; multidentate, with masticatory margin entirely opposite; apical portion straight to strongly curved ventrally; basal margin from slightly curved to conspicuously concave, clypeomandibular space absent to present in varying degrees. Compound eyes relatively developed. Antennae with 12 segments; scape dorsoventrally flattened, with external margin forming biangulate basal lobe followed by a crenulated lamella; antennal club moderate to conspicuous, with last two funicular segments usually distinct. Mesosoma robust or elongate; in lateral view, promesonotum continuously convex to strongly projected caudad; metanotal suture present, broad. Dorsal margin of propodeum slightly sloping upwards at its posterior portion; slope margin from slightly to abruptly oblique. Propodeum armed with triangular or tapered projections, slightly lamelliform and connected by a transverse carina usually slightly curved upwards. Petiole pedunculate; dorsal margin with rounded, low or weakly bulged node; subpetiolar process with different configurations, from absent to multidentate.

Queen Similar to conspecific workers, with modifications peculiar to that caste. Ocelli present. In dorsal view, mesoscutum slightly elongated, anterior portion cuneiform; notauli inconspicuous to weakly marked; parapsides generally oval, shallow to deep impressed; parapsidal lines somewhat shiny and slightly conspicuous to obsolete, involved by integumental sculpture; scutoscutellar sulcus from strongly to lightly impressed; pre-scutellum narrow, central portion relatively indistinct; axillae projecting posteroventrally, curved and hook-shaped; mesoscutellum transversely subrectangular to ellipsoid, posteriorly inclined, posterior margin concave. Metanotum visible, slightly projected. Wings usually light brown; pterostigma present in the forewing, distinct and brown to dark brown. Fore wing with longitudinal veins C (costa), Sc (subcosta)+R, M+Cu, 1A (anal), Rs+M, Rs (radial sector) and R1 (radius); the Sc+R vein extends from its posterior half to near the front of the pterostigma in tubular form; M+Cu with spectral basal portion and anterior half tubular; anal vein usually with anterior portion tubular; Cu usually tubular, extending posteriorly nebulously; radial sector with nebulous apical portion, not meeting R1; R1 usually reaching the most distal point of the wing margin; anterior portion of the radial sector varying in size. Vein M tubular and oblique, length variable; Rs+M straight or moderately curved, usually tubular, M (media) usually tubular in its anterior half, extending nebulously to the wing margin; Cu similar to M. Transverse veins: cu-a generally tubular, connecting the anal vein with M+Cu just after half of the anal vein, near or right after the branching point; 2r-rs tubular connecting the pterostigma near its median region to the radial sector; Rs connecting the Sc+R veins to the M and Rs+M veins and marking the breakpoint of the latter two, varied 1m-cu vein: absent as an appendage of the Rs+M vein or reaching Cu, closing the discal cell. Hindwing with longitudinal veins Sc+R, M+Cu and 1A; Sc+R briefly extends into a tubular shape after the point of connection with the M+Cu vein as the Sc+R1 vein and extends in the spectral shape to near the distal margin of the wing; anal vein usually tubular; Cu as a tubular appendage either partially or entirely spectral; Rs+M as short tubular appendix and other spectral length or absent; cu-a and 1r-rs+M transverse veins present: the first connecting the anal and M+Cu veins near the median portion of this first; the second connecting Sc+R and M+Cu near the distal portion of these veins. Five to eight submedian hamuli present.

Male Known Basiceros males are slightly smaller than conspecific gynes. Dark in color, with lighter appendages, from brown to dark brown. Integument mostly punctuate, punctuate-reticulate or foveate; some portions subopaque and slightly granulate, like the appendages; rugulae present near the head vertex, behind the compound eyes and with variable presence on the interocular space; sparse rugulae in the posterior half of the mesonotum and on the propodeum sides; mesopleuron differentially shining: either just at the mesoanepisternum with rest of the mesopleuron granulate, or much of the mesoanepisternum plus part of the mesokatepisternum shiny. Pilosity largely fine, filiform; suberect to subdecumbent, from yellow to brown. Head with maximum width close to the eye insertion; vertexal margin convex; cephalic capsule projected posteriorly, forming a variable conspicuous neck; occipital margin lamelliform and longitudinally costulate, varying in relation to the shape of the head (piriform or subpiriform). Compound eyes convex and prominent, ocelli protruding forming a cephalic crest in different degrees. Mandibles developed, triangular; external margins convex, curving apically; masticatory margins with 9–14 subtriangular teeth; basal margins with morphology similar to that of conspecific females, more or less concave with mandibles closed, leaving or not a clypeomandibular space. Clypeus ample, frontoclypeal portion slightly truncated or bulged, extending to the level of the frontal lobes; anterolateral portion depressed, concave; anterior margin lamellar, yellowish or slightly translucent, straight or medially concave medium, laterally rounded. Frontal area variably distinct, semicircular or transverse; slightly rugose or with a frons carina which extends more or less posteriorly towards the median ocellus. Frontal lobes salient, free margins sharply rounded in front; antennae inserted into their ventral face. Antennal scrobes deep and ellipsoid, delimited by a crenulate border and advancing to the lateral clypeal area. Postgenal carina continuous or almost continuous, irregular, extending from the posterolateral corner of the head to the mandibular insertion. Antennae long and filiform, with 13 segments. Scape short, about twice as long as wide; basal margin oblique and sharply rounded to the external margin, obtuse angle in the inner margin; apex truncated. Antennomeres 2 and 3 approximately half the length of scape; other funicular segments longer than wide; apical segment longer; antennal segments 8 and 9 slightly or conspicuously twisted, causing the antenna to appear to be twisted around its axis to varying degrees. Mesosoma robust, more or less elongated; pronotum anteriorly divided or not in two distinct portions; mesoscutum like conspecific gynes, presenting a longitudinal carina anteromedially, more or less distinct. Notauli complete, shallow or deeply impressed, extending after their converging point in variable fashion towards the scutoscutellar sulcus. Parapsides generally deeply marked, more or less oval; parapsidal lines shiny and distinct. Axillae projected as in the conspecific gynes, hook-shaped. Mesoscutellum in dorsal view shaped like an inverted “U”, posterior margin concave. Propodeum with posterior angles projected, projections either obtuse or slightly triangular, divided by strong transversal carina. Propodeal lobes auriculate. Metanotum narrow, medially projected. Petiole with morphology similar to conspecific females; petiolar spiracles projected laterad in the median portion of peduncle. Gaster in dorsal view with five visible segments. Genitalia (after Feitosa et al. 2007): genital capsule slender; parameres slightly enlarged, strongly rounded and with tips curved inward; in lateral view, abruptly narrowed toward the apex, volsella with the general pattern observed in Myrmicinae males; pygidium and subgenital segments with apical portion slightly narrow and rounded. Legs slender; calcar of strigil short and pectinate, present only on prolegs. Brownish wings; forewings with venation similar to conspecific gynes (varying regarding the length of transversal vein 1m-cu, that can be present as a short appendage on males and absent on gynes), with the following configuration: absent, obsolete (as a short appendage to Rs+M) or complete, closing the discal cell. Hindwings with tubular longitudinal veins Sc+R; M+Cu and 1A (anal), the former branching to short vein SC+R1 after the abscissa of Sc+R and M+Cu; Rs+M present as a short appendage after the abscissa of Sc+R and M+Cu. Anal vein short, apex slightly curved upwards, meeting cu-a; 4–8 submedian hamuli present.

Taxonomic Notes

All taxa of genera Eurhopalothrix, Octostruma, Protalaridris, Rhopalothrix and Talaridris were combined in Basiceros, sensu Baroni Urbani & De Andrade, 2007: 90-93. Synonymy of all basicerotine genera under Basiceros, by Baroni Urbani & De Andrade, 2007: 88, is incorrect procedure as Rhopalothrix has priority. Basicerotine genus-rank taxonomy documented in Bolton, 2003: 183-185, is retained.

References