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Worker measurements in mm (holotype-paratype). TL 2.61-2.64; HL 0.75-0.76; HW 0.71-0.72; IFW 0.35-0.35; ScL (only for holotype) 0.65; HWL 0.46-0.44; MeL 0.94-0.93; PLL 0.13- 0.17;. PPL 0.34-0.37; GLL 0.75-0.73; HfL 0.85-0.84.
Worker description: Brown-yellowish, with the head's frontal region, tergum I and sternum I of gaster darker; the dorsum of the head being darker than all other body parts. Integument finely reticulated throughout the body. Scattered short hairs all over the body and appendages, slightly curved at tip; longer ones confined to hypostoma, median region of clypeus, and on mandibles, in special on the mandibular apexes.
Head in full face view (Fig. 1) a little longer than broad (CI 95). Outer border of mandible straight; masticatory margin with apical, subapical and 4 triangular teeth, gradually diminishing in size towards base. Clypeus divided transversally by a ridge (better seen under the SEM; see also Fig.4), from where the clypeal setae arise; median seta distinct from anteclypeal seta; latero-median area of clypeus with a sharp triangular tooth at each side. Frontal area shallowly impressed. Frontal lobe semicircular, moderately approximate (FLI 49), with smooth free border. Frontal carina ending just after the expansion of the frontal lobes, parallel. Preocular carinae conspicuous, straight in front of the eyes, curving obliquely towards the heads median line, ending a little after the level of the frontal carinae ends. Vertex margin in full-face view strongly notched in the middle; the head posterior corners inflated. Inferior corner of occiput, in side view, more or less angular, emmarginate. Eye bulging, surpassing the lateral border of the head, with about 11 facets across greatest diameter. Antennal scape projecting beyond the tip of the head's posterolateral corner by a distance which exceeds its maximum width; the distal three fourths of scape gently incrassate. Only funicular segments I and VIII-X longer than broad, the others sub-equal in size and width.
Mesosoma (Figs. 2-3). Dorsal and lateral faces of pronotum not separated by a carina, emmarginate, with low and blunt triangular projections at the meeting of these faces; anteroinferior corner of pronotum with a rounded tooth; inferior margin smooth; paired median pronotal teeth separate, conical and blunt. Mesonotum with two very low, wide, flat semicircular tumuli anteriorly, divided by a depression, followed by a widely spaced pair of minute triangular projections and then by a more approximate, not so low, pair of blunt projections; posterior margin oblique in lateral view. Metanotum indistinct, not constricted in dorsal view. Basal face of propodeum emmarginate, with 2 or 3 low rounded unconnected projections; triangular propodeal spine very low, truncate and blunt. Hind femora shorter than mesosoma length.
Waist and gaster (Figs. 2-3). Dorsum of petiolar node without ridges, ascending in lateral view towards two spaced faint projections, bearing each a pit and its hair; petiole broader than long in dorsal view. Postpetiole as long as broad in dorsal view, dorsal and posterior margins straight, in lateral and dorsal view, respectively; dorsally with a swallow impression, near the posterior margin. Gaster, when seen from above, rather suboval, posteriorly rounded. Tergum I without longitudinal keel or furrow. Sternum I without a sagital keel.
Gyne and male: Unknown.
Holotype and paratype workers: BRAZIL, Pará State: Santa Maria das Barreiras , Rio Araguaia , 30. ix.2005, R.R. Silva & R. Feitosa cols (deposited in Museu de Zoologia da Universidade de Sao Paulo). The workers were collected manually while foraging outside the nest, in a beach along the West bank of the Araguaia river, part of the Amazon River drainage.
Comments: According to R. Feitosa field book (our translation from Portuguese) "the ants were collected at midafternoon of a cloudy day. In spite of the heavy rains of the preceding days (onset of the rainy season) the river water level was relatively low; leaving exposed a wide sand strip, with scattered bushes. The banks in this particular place are covered by gallery forest. The ants were found moving slowly towards their nest opening, which consisted of a single rounded minute opening in the sand, without any mound or crater. We waited for some minutes for other ants to come out from the nest, but they did not show up. Close to this nest, we found a nest of Mycetophylax emeryiHNS and of an unidentified DorymyrmexHNS ".
Additional geographic distribution. We have recently studied MycetagroicusHNS material not available at the time we described the genus: two workers of M. cerradensisHNS from Paraguacu Paulista, SP, Brazil, collected by Eduardo Arrivabene Diniz, and M. triangularisHNS workers from Uberlándia, MG collected by Heraldo Vasconcellos. Both samples are deposited in the Colecao Entomológica Costa Lima of the Universidade Federal Rural do Rio de Janeiro. Ramos et al. (2003) reported the occurrence of M. cerradensisHNS in Bom Despacho, MG. These new records support the original statement that MycetagroicusHNS is a typical inhabitant of the Cerrado biome, although sometimes in gallery forests, but mostly in stricto senso Cerrado.
Found most commonly in these habitats: 2 times found in galery forest.
Found most commonly in these microhabitats: 2 times sandy river bank.
Collected most commonly using these methods: 2 times nest excavation.
Elevations: collected at 164 m