Mycetomoellerius opulentus

Colonies form nests in the ground, with an entrance in the form of a soil turret that can be up to 15 cm high.

Identification
Mayhé-Nunes & Brandão (2002) - T. opulentus differs from Trachymyrmex dichrous, Trachymyrmex compactus and Trachymyrmex relictus in the strongly projecting and hornlike apex of the antennal scrobe. The strongly spinous antero-inferior corner of pronotum and the straight, not excised postero-dorsal border of the postpetiole separate it at once from T. dichrous and T. compactus. Additional differences from T. relictus consist in the low and tumuliform lateral pronotal projections, shorter than the anterior mesonotal ones, in the very short propodeal spines, and in the practically unarmed dorsum of the petiolar node.

Variation: A worker from Guiana (=Trachymyrmex wheeleri) differs slightly from the syntypes from Honduras by the vestigial third pair of mesonotal projections, the bigger hom-like projections at the apex of the antennal scrobes, and the smaller propodeal spines. These characters also shown some variation in the other samples examined. Workers from the Venezuelan samples have less produced antennal scrobes apices.

Distribution based on Regional Taxon Lists
Neotropical Region: Costa Rica, Guyana, Honduras, Mexico, Panama.

Biology
Mayhé-Nunes & Brandão (2002) - The first information is from Mann (1922:49) on the type series: “... large colony. The nest was in the ground, alongside a trail in thick woods. The entrance was in the form of a turret, loosely constructed of earth and about 6 inches in height; a foot beneath the surface was a large cavity, containing a fungus garden, pendulous and 4 or 5 inches in diameter.” Gabriel A. R. Melo has collected in Manaus three workers following a forage trail, carrying dry leaves (personal communication, recorded in Mayhe's notebook #105). Antonio Mayhe and Jose V. Hernandez found two nests in Aroa, Venezuela, in a secondary forest, at 865m of altitude. The entrance of the first (Mayhe’s notebook #143) was at the side of a human trail and presented a turret made by rigid earth coming out of the litter, 1cm diameter and 3 cm height; the unique chamber was 20 cm deep. The second one (Mayhe's notebook #152) presents also a turret, although smaller, and its unique irregular chamber was 16 cm deep, with the fungus garden hanging from the roof. Due to the intricate root system around both nests, it was impossible to study their architecture. The ants feign death when disturbed, in a conspicuous cryptic behavior.

Nomenclature

 *  opulentus. Sericomyrmex opulenta Mann, 1922: 48, fig. 21 (w.) HONDURAS. Combination in Trachymyrmex: Weber, 1958b: 51. Senior synonym of wheeleri (and its junior synonym pakeelai): Mayhé-Nunes & Brandão, 2002: 680.

Worker
Mayhé-Nunes & Brandão (2002) - TL 5.1-5.8; HL 1.03-1.27; HW 1.03-1.19; IFW 0.65-0. 76; ScL 0.89-1.00; TRL1.59-1.87; HfL 1.40-1.59. Uniformly ferruginous. Integument finely reticulate-punctate, opaque. Long, dense, flexuous hairs abundant on head, alitrunk and waist, where they are more or less strongly curved throughout, curved only at base but more or less decumbent on gaster, oblique to subdecumbent on scapes and legs. Dense, very short and fine pubescence of lighter color curved or inclined on head, alitrunk, waist and gaster, appressed on scapes and on legs, on the latter also on the extensor face.

Head. Mandibles either finely striate, except on apical third which is smooth and shining or nearly smooth; masticatory with apical tooth and approximately 9 teeth, gradually smaller towards the mandibular base. Frontal lobes subsemicircular at apex, but anteriorly more or less narrowed and drawn out forward along the posterior half of median apron of clypeus. Frontal carinae diverging caudad, fading out just in front of the horn-like and projecting apex of antennal scrobe. Preocular carinae not curving mesad above eyes, continuing straight backwards, and becoming faint on posterior third but nearly reaching the apex of scrobe which is distinctly delimited both mesially and laterally except by the horn-like apex. Supraocular tumulus usually well developed, tumuliform. Occiput in full-face view distinctly notched in the middle. Paired carinae of vertex blunt but distinct, curving laterad in front, joining the frontal carinae. The longitudinal impression between these carinae extends laterad in front, forming a transverse groove across the frons just behind the frontal lobes. Occipital tooth usually inconspicuous in the form of a very low and blunt tumulus. Eyes moderately convex, with about 12 facet rows across the greatest diameter. Antennal scapes shorter than length of head capsule. but their apex either attaining or distinctly surpassing the horn-like tip of the scrobe when lodged in the same. All funicular segments distinctly longer than broad.

Alitrunk. Pronotum with an inconspicuous humeral tumulus on each side; the antero-inferior corner strongly spinous; the lateral spines of the pronotal dorsum in the form of low and blunt tumuli; the mesial teeth vestigial or absent. Mesonotum with a pair of stout anterior conical spines, facing obliquely laterad, followed by a pair of much lower, multituberculate tuberosities facing caudad, the third pair of mesonotal projections similar to the second but much smaller and lower. Alitrunk shallowly impressed at metanotal groove. Basal face of propodeum narrow, bordered at each side by a low denticulate ridge; propodeal spines very low, pointed or subrectangular. Hind femora shorter than length of alitrunk.

Waist and gaster. Petiole pedunculate, the node proper as seen from above slightly longer than broad, the dorsal face with a pair of very faint, longitudinal and tuberculate ridges, practically unarmed; supetiolar process absent. Postpetiole broader than long, its dorsum shallowly excavate both postero-mesially and postero-laterally between two very broad and blunt, posteriorly diverging ridges; the posterodorsal border straight. Gaster opaque; tergum I with a shallow sagittal groove flanked by a pair of broad, low, and rather indistinct median ridges, the sides distinctly marginate by lateral ridges, shallowly excavate below these ridges; the dorsal surface rather densely covered with piligerous tubercles, connecting rugulae between these tubercles either absent or vestigial or quite distinct.

Queen
Mayhé-Nunes & Brandão (2002) - TL6.4; HL 1.35; HW 1.27; IFW 0.81; ScL 0.95; TRL2.03; HfL 1.62. Color, sculpture, pilosity, pubescence, and diagnostic characters as in worker. The following should be noted: Ocelli small, the antero-median ocellus just behind the transverse groove in front of the strong, paired vertical ridges; the lateral ocelli placed on the outside of these ridges, facing laterad. Occipital tubercle well developed and of approximately the same size as the supraocular tubercle. Tip of antennal scapes not quite attaining the apex of the hornlike posterior projection of the scrobe, when lodged in the same. Pronotum with a pair of low and truncated subtriangular scapular spines, tumuliform with blunt apex directed out and forwards. Mesoscutum without notable dorsal projections. With the alitrunk in oblique dorsal view, shallow parapses delimited by the parapsidial furrows; mesothoracic paraptera impressed. Mesonotal scutellum with a longitudinal groove, the posterior end distinctly bidentate, the blunt teeth directed backwards with parallel sides. Propodeal spiracles orifices visible, spines short, toothlike; the basal face longitudinally excavate between the teeth and subcontinuous with the declivous face. Petiolar node proper distinctly broader than long. Dorsum of tergum I of gaster coarsely reticulate-rugose. Wings unknown.

Type Material
Mayhé-Nunes & Brandão (2002) - Worker; Honduras: San Juan Pueblo. Worker lectotype and 11 workers paralectotypes of T. opulentus, (here designated, examined); worker syntype (“cotype”) of T. wheeleri, MZSP (examined).