Most collections of Cyatta abscondita are from Cerrado localities, including Fazenda Água Limpa and IBGE (Brasilia, DF), Fazenda Olho D'Água and RPPN do Acangau (MG), and Broa preserve (SP). Some specimens of C. abscondita have been taken outside the Cerrado biome, including Caatinga (a biome characterized by deciduous thorny woodland vegetation) in RPPN Serra das Almas (CE), and in fragments of semideciduous forests in northwestern São Paulo state.
Foraging behavior. Foraging workers of Cyatta abscondita are difficult to locate because colony sizes are small, workers forage individually, and individuals are very small and cryptic. In mid-September, which coincides with the beginning of the rainy season at FAL, three to four individuals from three different nests were observed foraging at night between 22h and 23h. In February and April, at the end of the rainy season, ants were likewise observed foraging individually only after sunset. Only in one case at FAL were workers observed to forage in the early afternoon on two consecutive days in April between 13h and 15h during a time when the nest entrance was shaded from direct sunlight. Unlike the other nests, this nest occurred in a well-watered, human-managed grassy lawn. Nests collected in July at the height of the dry season at the Broa preserve in São Paulo State, were located in the shade and, unfortunately, neither foraging nor nest-building activity was observed. The entrance of one nest at FAL was located ~4.5 centimeters from the entrance of an adjacent Mycocepurus goeldii nest. At around 23h a Cyatta abscondita worker was observed lurking slightly inside the nest entrance while workers of M. goeldii foraged on bait placed near the nest entrances. When M. goeldii workers were absent, the C. abscondita worker darted out to retrieve a piece of bait and quickly returned to its nest. This lurking and rapid foraging behavior was repeated until the supply of bait was depleted. In rare cases of contact between C. abscondita and M. goeldii workers, C. abscondita workers were observed to remain motionless. Aggressive interactions were not observed.
Nest architecture. At FAL, nest entrances of Cyatta abscondita consisted of a single, inconspicuous, hole in the ground of approximately 1 mm in diameter without any accompanying mound or turret. As mentioned above, the entrance of one nest was located in the mound of a Mycocepurus goeldii colony ~4.5 cm from the M. goeldii nest entrance. At the Broa preserve, nest chambers of C. abscondita were encountered serendipitously while excavating M. goeldii nests and the nest entrances were not observed. Nests contained three to eight chambers. In several nests chambers were roughly arranged vertically below the nest entrance, although it is possible that additional, laterally dispersed chambers were missed during the excavations. The shallowest chamber encountered (FAL) was 29 cm deep and the deepest chamber (Broa) was 195 cm deep. Because no gynes were found during the nest excavation at Broa, it is entirely possible that additional chambers occurred below a depth of 2 meters. Chambers were elliptically shaped, 1–2.5 cm wide and 2–5 cm high. The largest garden chamber encountered (FAL) was 2.5 x 5.5 cm; at Broa, a similarly sized chamber contained ~50 hanging garden filaments. Some chambers were empty; in one case, an empty chamber contained three polydesmid millipedes.
Garden morphology. Gardens were pendant and arranged in filamentous curtains suspended from the chamber ceiling, similar to the fungus gardens of Mycocepurus species and of Kalathomyrmex emeryi (TRS, JSC, pers. obs.). Single fungal curtains were 5–6 mm long and 1–2 mm wide and a maximum number of 50 curtains were found in a single chamber. Curtains were directly attached to the soil of the chamber ceiling rather than to rootlets. In one nest maintained in laboratory culture for three months, workers attached garden filaments to the plastic ceiling of the nest box and cultivated suspended gardens. The filaments were firmly attached to the plastic ceiling by an unknown mechanism.
Worker description. Holotype (Paratypes, n=9). TL 2.40 (2.29–2.56), WL 0.62 (0.58–0.65), HL 0.53 (0.50–0.55), HW 0.48 (0.48–0.51), SL 0.48 (0.43–0.50) ML 0.34 (0.32– 0.36), EL 0.13 (0.12–0.13), PL 0.17 (0.14–0.19), PPL 0.22 (0.20–0.24), GL 0.52 (0.49–0.64), CI 90 (90–95), SI 101 (90– 100), MI 64 (63–68), FLD 0.17 (0.17–0.18).
Head. in full-face view subrectangular, slightly longer than wide (CI 87–95); sides subparallel. Mandible subtriangular with four well-developed teeth; apical tooth twice as large as subapical tooth; diastema between subapical tooth and 3rd tooth shorter or slightly shorter than diastema between 3rd and 4th teeth; dorsum of mandible reticulate and with appressed hairs; masticatory margin of mandible, including apical tooth, smooth, shining, and darker in color than rest of head, with long, simple hairs. Clypeal apron (anteclypeus) convex to almost triangular, smooth, and shining; unpaired median setae (length 0.07–0.10 mm) originating slightly before (anterior to) posterior edge of clypeal apron and almost or as long as antennal pedicel, not reaching apex of mandible; clypeus with pair of lateral transverse carinae, each extending from below frontal lobe to mandibular insertion. Medially these carinae developed into lamellae perpendicular to clypeal face, thus forming a wall that divides the clypeus laterally into anterior and posterior areas, very likely homologous with clypeal morphology of closest relative, Kalathomyrmex emeryi; medially clypeus is not so divided, face extending posterad between frontal lobes. Frontal lobes reduced, convex, barely covering antennal insertions. Frontal carina fading out posteriorly at midlength of compound eye. Well marked triangular area with concave anterior margin between frontal lobes reticulate, bordered anteriorly by rounded finger of clypeus, which extends broadly posterad between frontal lobes. Compound eye set slightly before middle of head, with 7–9 ommatidia at maximum length and 6 ommatidia at maximum width (33–47 ommatidia in total). Antennal scape covered with minute, simple, appressed hairs; antennal scape wider at seven-tenths of its length, and slightly surpassing posterolateral corners of head when laid back over head capsule; first funicular segment (pedicel) slightly longer than or as long as second and third funicular segments combined. In full-face view, cephalic margin deeply notched medially (i.e., at vertex) and rounded laterally, shallow vertexal sulcus extending medially towards frontal lobes, fading at eye level; in lateral view, ventral face of head slightly convex. Hypostomal teeth absent. Palp formula 4,2.
Mesosoma. Profile of promesonotal dorsum in lateral view distinctly tuberculate, tubercles attenuate and blunt. In dorsal view, promesonotum with raised shield-like area, broad anteriorly and narrowing posteriorly, distinctly separated from lower, lateral promesonotum; raised area formed anteriorly by triangular lateral pronotal tubercles and two median low and approximate pronotal tubercles and posteriorly by eroded remnants of promesonotal tubercles; lower, lateral area of promesonotum in dorsal view subtriangular, broader and anterolaterally angled anteriorly; in lateral view, inferior corner of pronotum rounded, lacking spines or angles. Anepisternum indistinctly separated from katepisternum. Metanotal groove relatively broad and strongly impressed, in lateral view extending to antero-ventral margin of metapleuron. Metapleura ventrally with two spiniform processes between mid and hind coxae, best seen by removing hind legs. Basal (dorsal) face of propodeum in lateral view a low, rounded, protuberance posterior to metanotal groove; in dorsal view, basal face very small, raised above remainder of propodeum, and narrowing anteriorly; declivous face of propodeum behind protuberance concave; propodeal spines triangular, obliquely directed upwards and strongly diverging in dorsal view; declivity of propodeum much longer than base (dorsum); propodeal spiracle opening in an angle of 45° in relation to main body axis; in lateral view, propodeal lobes rounded without posterior projections.
Metasoma. Peduncle of petiole vestigial; in lateral view, petiolar node well developed, subquadrate, with anterior face almost straight and vertical; dorsum of petiolar node short and almost flat, meeting vertical posterior face in slightly rounded angle; ventral face of petiole slightly concave or straight medially, lacking petiolar process; in fronto-dorsal view, node of petiole shallowly V shaped, dividing node into a pair of rounded tubercles. Postpetiole robust, almost twice as long as petiole and slightly less than 0.5x gaster length; in dorsal view, postpetiole subtriangular, anterior margin rounded, lateral margins slightly diverging posteriorly; posterior margin with deep median impression, forming two distinct small lobes; in lateral view, anterior portion of postpetiole convex, postpetiole relatively compressed dorsoventrally; ventral projections absent. In profile, gaster elliptical and dorsally finely reticulo-striate; in dorsal view, apical margin of pygidium (gastral segment IV, i.e., abdominal segment A7) medially emarginate, bilobed; gastral sternite IV (hypopygium, i.e., A7) covered with simple decumbent hairs; in lateral view, pygidium rounded, laterally overlapping and concealing the hypopygium; pygidium weakly reticulate and shiny; in ventral view, pygidium posteromedially emarginate (i.e., V–shaped), the triangular hypopygium fitting within the emargination of the pygidium. Sting apparatus present, protruding through emargination on pigydium.
Color pale yellow to light brown; antennae, mandibles, and legs lighter than rest of body. Body integument areolate, with short appressed simple hairs, appearing almost hairless.
Gyne description. TL 3.27–3.32, WL 0.86–0.87, HL 0.65– 0.66, HW 0.60–0.63, SL 0.56, ML 0.41–0.42, EL 0.16–0.17, PL 0.25–0.28, PPL 0.29–0.30, GL 0.79–0.81, CI 91–96, SI 89–93, MI 62–65, FLD 0.20–0.21 (n=2).
As in worker description, but with caste-specific morphological differences as follows. All gynes studied are dealate.
Head. Eyes large, with 10–11 ommatidia in maximum length and 9 ommatidia in maximum width, ~65 ommatidia total; median ocellus rounded, located in a median sulcus extending almost from the occipital carina in the back of the head to the middle of the frons; integument surrounding ocelli darker in color than elsewhere. Clypeus with unpaired median seta arising on short transverse wrinkle-like ridge that crosses clypeal apron; two to four short simple appressed hairs on clypeal apron on each side of median clypeal seta. In full-face view, cephalic border with median (vertexal) notch, not as deep as in worker. Mandibles dorsally coarsely rugose.
Mesosoma. Pronotal dorsum conspicuously areolate, lacking anterior pronotal tubercles; lateral pronotal tubercles present, blunt and small; humeral pronotal tubercles vestigial. Mesoscutum, in dorsal view, rounded to slightly ovate and overall reticulo-rugose; dorsum of mesoscutum, in profile, almost flat; mesoscutal sulcus, in dorsal view, short, not extending more than 1/4 length of mesoscutum; notauli absent; parapsidal lines short, inconspicuous, and extending nearly to lateral margin of mesoscutum; transscutal suture conspicuous. Scuto-scutellar sulcus deep and with ~7 transverse carina; margin of axilla rounded, dorsally reticulo-rugose. Scutellum posteriorly weakly bidentate, dorsally rugose and with a shallow median longitudinal groove. Anapleural sulcus deep, with transverse carinae, dividing mesopleuron into anepisternum and katepisternum. Metanotal groove extended into a complete metanotal-propodeal suture. In profile, metanepisternum present, small. In profile, metanotal groove conspicuous, continuous with mesometapleural suture. Ventral metapleural processes present as a pair of spiniform tubercles between the mid and hind coxae, similar to, but longer than, those present in worker. Propodeum with pair of short, right- angled denticles; dorsum, lateral margin, and declivity of propodeum reticulate.
Metasoma. Petiole as in worker. Dorsum of postpetiole reticulo-rugose. Dorsum of gastral tergite IV (A7) rugulose; pilosity as in worker; gastral tergite and sternite IV (pygidium and hypopygium; A7) as in worker.
Male description. EL 0.25, EW 0.27, FL 0.81, FLD 0.21, GL 0.87, HL 0.58, HW 0.73, IOD 0.42, ML 0.21, MI 37, PL 0.27, PPL 0.25, PPW 0.38, PrW 0.54, PW 0.21, SL 0.54, TL 3.21, WL 1.04, CI 126, SI 127 (n=1).
A medium-sized male with head large relative to size of the mesosoma. Mandibles broadly triangular, apical and subapical teeth present large; remaining tooth minute, indistinct; texture coarsely granulate. Palp formula 4,2. Clypeus broadly trapezoidal in frontal view; anterior margin convex, with a long median seta (0.11 mm) originating at the anterior margin and projecting over the mandibles; in lateral view anterior margin of clypeus forming a lamella projecting over the mandibles. Frontal lobes triangular, only partly covering the condylar bulbs of the scape in full face view. Antennae with 13 segments; scape surpassing the posterior border of the head by 1/3 of its length. Antennal funicular segment II (0.08 mm) almost as long as funicular segment I (pedicel; 0.11 mm) (Figures 3a,b). Eyes conspicuously large, at maximum diameter approximately half as long as the entire head, counting ~15 ommatidia in maximum width and ~23 ommatidia in maximum length. Ocelli large, elevated above the remainder of the head. Surface of head coarsely granulate, finely rugulose around the ocelli.
Mesosoma. Tergum of promesonotum not distinctly enlarged, giving the mesosoma a rather slender appearance in lateral view. In dorsal view, lateral pronotal teeth pyramidal, twice as wide at the base than high, with sharp tips. Propodeal spines reduced to broad teeth with rounded tips.
Metasoma. Anterior peduncle of the petiole about the same length as the petiolar node. Postpetiole wider than long; trapezoidal in dorsal view; posterior margin slightly concave. In lateral view, postpetiole with a broadly rounded ventral lobe. Reticulate sculpture on gaster finer in appearance than on the remainder of body, which tends to be areolate; gastric tergites moderately lustrous; rest of body with a weak silky shine. Body surface sparsely covered with short appressed setae, only ventral side of postpetiole with 10 erect setae. Body dark, blackish brown; legs and antennae slight lighter in color, yellowish to dark brown. Forewings with closed basal (BC), costal (CC), submarginal (SMC1), marginal (MC), and subbasal (SBC) cells; submarginal cell 2 and discal cell 2 open (Figure 3d). Hindwings with closed basal cell and open marginal subbasal and discal cells (Figure 3d). Left forewing with closed discal (DC1) cell, whereas the right forewing lacking this cell. The presence of a closed discal cell in the forewing is, so far as is known to us, unique in the Attini; this character is absent in all other attine genera, including the closest relative of C. abscondita, Kalathomyrmex emeryi. A closed discal cell is plesiomorphically present in many ant species, including those in genera closely related to the Attini such as the Blepharidattini, Cephalotini, Dacetonini, and Pheidolini.
Larva. Description based on SEM study of two specimens, late- (probably fourth) instar larvae of uncertain (but probably worker) caste. Due to collapsed condition of specimens, habitus profile could not be characterized with certainty, but is consistent with the "attoid" profile category of Wheeler & Wheeler [1976], i.e., with a moderately curved, ventrally shortened profile. Thoracic-abdominal articulation apparently absent, thoracic intersegmental constrictions superficial, deep lateral depressions associated with abdominal spiracles absent, all states shared with other Attini. Remarkably, body hairs present dorsally and laterally, a condition otherwise common in the Myrmicinae but rare in the Attini, in which larvae usually lack dorsal and lateral hairs. In the Attini, such hairs are known to be present only in the larvae of Mycocepurus goeldii and M. smithii [Schultz & Meier 1995], where their presence may be plesiomorphic, and in Sericomyrmex and some Acromyrmex species, where their presence is likely secondarily derived. Predominant hair type bifurcate with "anchor tips." Two rows of dorsomedian, very long anchor-tipped hairs present. Labrum monolobate, narrow, bulging. Anterior setae present as papillae. Mandibles typically attine: short, fleshy, subconical. A distinct, undivided apical mandibular tooth and no subapical teeth; spinules evenly distributed on all mandibular surfaces. Mandibular gnathobases absent. Basal portions of maxillae fused with head capsule. Maxillary palp widely removed laterad from galea, a synapomorphy for the Neoattini. Galea reduced, present as two sensilla surmounting a low protuberance, as in all Attini except for some Myrmicocrypta species. Maxillary palp digitiform, maxillary accessory palpal sensillum absent. A single seta present laterad of maxillary palp, a character shared with Mycocepurus species. As in most attines, labium feebly protruding, lateral sericteral protuberances absent, labial palps digitiform. Labial spinules present on anterior surface slightly dorsal to the sericteries. Hypopharyngeal spinules multidentate and apparently densely distributed. On the head, genal lobes absent, a state in the Attini shared with Myrmicocrypta, Apterostigma, Mycocepurus, and Mycetarotes species. Supra-antennal setae present and abundant, a condition common in the subfamily but otherwise present in the lower Attini only in M. goeldii. Subantennal (genal) setal arrangement plesiomorphic for the tribe, consisting of around 12 setae on each gena. Supraclypeal setae present and setiform. Two clypeal setae present. Spinules absent on the head dorsad of the labrum, the state common to most attines. Due to the poor condition of specimens, most ventral thoracic/abdominal characters could not be studied, including the presence/absence of: leg vestiges, prothoracic food anchor, ventromedian protuberances on various segments, papilliform spinules, and hairs. Two setal sockets occur ventral of the anal opening on abdominal segment IX. No other setae are associated with the anal opening. Ventral anal lip absent.
Cyatta abscondita is the distant sister taxon of the genus Kalathomyrmex, and together they comprise the sister group of the remaining neoattine ants, an informal clade that includes the conspicuous and well-known leaf-cutter (parasol) ants. Morphologically, Cyatta abscondita shares very few obvious character states with Kalathomyrmex. It does, however, possess a number of striking morphological features unique within the fungus-farming tribe Attini, including mandibles of worker and gyne 4-toothed; in ventral view, metapleura of the worker and gyne with two spiniform processes between the mid and hind coxae; apical margin of the pygidium medially emarginate, V-shaped; the closed marginal cell on the forewing of the male. It also shares morphological character states with taxa that span the ancestral node of the Attini.
