Basiceros tumucumaquensis

Virtually nothing is known about the biology of this species. The type-series was collected below surface, close to tree roots, with the nest apparently scattered in indistinct chambers. RSP also collected two workers from a leaf litter sample taken around superficial roots of a Brazil nut tree (Bertholletia excelsa, Lecythidaceae). Those two workers were kept alive in laboratory conditions for three days, in which sparse interactions between specimens were observed. Workers moved slowly through the terrarium, with occasionally slow-paced antennation and showing thanatosis when disturbed. Unfortunately, all the conducted “cafeteria” experiments failed and specimens did not accept any items offered. Similarly, part of the type-series was kept alive in laboratory conditions for several weeks, consistently ignoring live prey dropped inside the terrarium, but sometimes accepting freshly-killed adult fruit flies.

Identification
Mandibles bizarre, apical portion strongly curved ventrally, basidorsal sulcus present, slightly transversal to mandibular dorsa, basal angle translucent. Clypeus densely covered with decumbent squamiform hairs. Head dorsum rugulose, with long clavate hairs.

Basiceros tumucumaquensis can be separated from other Basiceros species by the combination of mandibular and labrum morphologies and general pilosity on the worker, and by head and mandibular morphologies, pilosity, and mesosomal sculpture on the male. This new species is very similar to Basiceros scambognathus, from which the worker caste can be differentiated based on head shape and pilosity, body pilosity, mesosomal and gastral sculpture, and mandibular shape. The male of Basiceros tumucumaquensis looks like a chimera between males of Basiceros conjugans, Basiceros manni and Basiceros scambognathus. Body coloration is almost uniformly dark; mandibles are sinuous and not subtriangular like in B. scambognathus; the apical tooth follows the profile of the masticatory margin, not being projected as in B. scambognathus; the head is subpiriform, resembling other males of Basiceros — in B. scambognathus, it is subhexagonal.

In terms of variation, workers of B. tumucumaquensis present slightly variations in integumentary coloration and sculpture, pilosity density, and subpetiolar process, size, and slightly on labrum morphology — the cleft on distal margin can vary on extension and inner margin of lateral lobes can be more or less straight.

Distribution based on Regional Taxon Lists
Neotropical Region: Brazil.

Biology
The holotype and some paratypes of this species have oribatid mites on the ventral face of mandibles. It is not possible to confirm whether such arachnids are phoretic, commensal myrmecophiles or parasites.

Nomenclature

 * . Basiceros tumucumaquensis Probst & Brandão, 2022: 65, figs. 26-28, 32 (w.m.) BRAZIL (Amapá).

Type Material

 * Holotype worker: BRAZIL: Amapá, PNMT, 1.242333 -52.419778 ±10m, 132m, 25.xii.2018, R. Probst & O. Guilherme cols. (R. S. Probst #678) [MZSP, CASENT0647157].
 * Paratype workers: Same data as holotype [MZSP, 4 workers, CASENT0647158, CASENT0647159, CASENT0647160, CASENT0647161; MPEG, 2 workers,  CASENT0647162,  CASENT0647163;  DZUP,  one  worker,  CASENT0647164;  MCZ,  one  worker, CASENT0647165; JTL, one worker, CASENT0647166]. Paratype male: Same data as holotype [one male, MZSP, CASENT0647167].