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Holotype: Worker BRAZIL, Mato Grosso State: Gustavo Dutra GoogleMaps [15° 49' S, 55° 24' W], 25. x. 1953, RCG [C. R. Goncalves col.] # 1677 [ Goncalves GoogleMaps notebook], deposited at MZSP. GoogleMaps Notes: on the original label, the acronym for the collector is wrongly spelled as RCG. Information on this collector and locality, related however to different species, matches exactly the same information as for this sample (Brandao, 1990). Mayhe Nunes visited the area recently and found that Gustavo Dutra was the name of an Agricultural School, now a small village known as Sao Vicente, at the Santo Antonio do Leverger county, some 100 Km SE of the State capital, Cuiaba.
Fig. 12. Mycetagroicus triangularisHNS new species , worker paratype, Brazil, MT: Gustavo Dutra. Habitus in dorsal view. Fig. 13. Mycetagroicus triangularisHNS new species , worker paratype, Brazil, MT: Gustavo Dutra. Postpetiole and gaster in dorsal view.
Paratypes: 3 workers, same data as holotype (one specimen at each collection: MZSP - one intact plus one prepared for SEM; IBUS, USNM); one worker, BRAZIL, Distrito Federal: Brasilia GoogleMaps [15° 47' S, 47° 55' W], Fazenda Agua Limpa GoogleMaps "cerrado", 2. viii. 1988, T. Schultz col. TRS # 92 0802 03 (USNM) GoogleMaps; one dealated queen, BRAZIL, Bahia: Encruzilhada GoogleMaps [15°31' S, 40° 54' W], 960 m. xi. 1972, Seabra & Alvarengacol. # 8869 [ Kempf GoogleMaps notebook] (MZSP) GoogleMaps.
Etymology. The name was given in reference to the triangular shape of the clypeal teeth (Latin: triangularis).
Description. Worker. Measurements (in mm): TL2.72; HL0.80; HW 0.75; IFW 0.43; ScL 0.62; TrL 1.07; HfL 0.85. Colorbrown. Hairs all over the body, denser on antennae and legs.
Head (Figs8. 11). Mandibular external margin strongly rugulose (Fig. 11), irregularly sculptured in relation to M. cerradensisHNS (some 20 rugulae in a perpendicular line arising from the mandible external margin, at midlength) with an apical tooth and 7 regularly developed teeth; external margin straight from the base to the subapical tooth level, where it curves inwards. Clypeus (Fig. 11) lateral region near the base of frontal lobes with a triangular teeth, better seen in oblique view. Frontal area inconspicuous. Frontal lobes rounded, their largest width posterior to the antennal insertions, from where they curve inwards, forming a constriction. Frontal carinae slightly sinuous, fading well before reaching the occiput. Eyes with about 10 facets across the greatest diameter. Antennal scapes surpassing the occipital corners by near 5/6 of their chord length, when laid back over the head as much as possible. Only funicular segments I and VIII-X longer than broad, the other sub-equal.
Alitrunk (Figs 9-10,12). Height of pronotal anterior face shorter than in the other MycetagroicusHNS species (Fig. 10, compare with Figs 4, 19). Lateral pronotal spines triangular, projecting from lateral margin. Pronotum with a pair of short but conspicuous median projections, widely separated; antero-inferior corners (Fig. 9) angulated or each with a minuscule tooth at apex. Mesonotum without projections on anterior portion; middle of posterior portion with a relatively low triangular protuberance microscopically tuberculated. Anepistcrnum separated from katepistcrnum by a strong ridge. Metanotal groove shallowly impressed. Propodeum spiracle opening slit shaped in side view.
Petiole, postpetiole and gaster (Figs 9, 12-13). Dorsum of petiole with two faint longitudinal ridges; the node proper, as seem from above, slightly broader than long (Fig. 12). Postpetiole longer than broad in dorsal view. Gaster (Fig. 13) with irregularly spaced hair pits. Dorsal disk of the gaster without longitudinal keels.
Female (Figs 14-16). Measurements (in mm) TL 3.75; HL 0.91; HW0.94; IFW 0.51;ScL 0.66; TrL 1.38; HfL 1.00. Color ferrugineous brown, with the front of the head and gaster darker. Except by the short hairs on appendages, the whole body covered by moderately long curved or inclined hairs.
Head (Fig. 14). Very similar to those of the workers, except for the presence of three similarly developed ocelli; the presence of a distinct median longitudinal ridge posterior to the frontal area; and the more pronounced triangular clypeal projections.
Alitrunk (Figs 15-16). Pronotum without the median projections.
Scutum without noticeable divisions; anterior border with a small longitudinal ridge; parapsidal furrows in low longitudinal keels; parapscs slightly depressed, each with two minute transversal carinae. Mesothoracic paraptera impressed, with external borders smoothly rounded; the median area narrower than the lateral areas. Scutellum with two low and blunt tubercles; posterior margin with two close, flat and blunt spines, directed backwards; the distance among them at apices similar to their width at base. Metathoracic paraptera small and narrow (Fig. 16), covered by the scutellum spines in dorsal view. Propodeum with two big, blunt and flat spines, at the meeting of the basal and declivitous faces.
Petiole, postpetiole and gaster (Figs 15-16). Dorsum of petiole with two minute projections close to the posterior border. Postpetiole almost two times broader than petiole, shallowly impressed on the middle. Disc of the first gastric tcrgitewith pronounced rugulae, forming a conspicuous net; and a short longitudinal ridge at each side.
Biology. In his notebook, Goncalves recorded for sample #1677:
"Attini. subterranean nest", which is the only available information on the biology of this species. The dealated female was collected in November, at the onset of the rainy season in Eastern Brazil.
Comments. The triangular teeth or projections at the lateral areas of the clypeus readily distinguishes this species from all other known MycetagroicusHNS. The Fazenda Agua Limpa is a typical cerrado reserve that belongs to the Universidade de Brasilia, but the lack of further information on the exact collecting place in Encruzilhada, Bahia state, prevents us from deriving any conclusion on its distribution or preferred habitats.