Proceratium amazonicum

The single specimen of this new species was collected in soil at a depth of 10 cm in an area of 25x25 cm (TSBF trap, Anderson & Ingram, 1993). A soil sample was placed in a Winkler extractor for 48 hours. The material was obtained in the federal reserve of Floresta Nacional do Jamari (FLONA do Jamari) located on the grounds of the municipalities of Cujubim, Porto Velho, Ariquemes and Itapuã do Oeste, in the state of Rondônia, Brazil.

Identification
Fernandez et al. (2019) - A member of the micrommatum clade. Frontal triangle on head elevated; mandible with 4 denticles (including the apical tooth); propodeal tumulus narrow and high; long, erect or suberect hairs on petiole and dorsum of abdominal segment III; large species TL: > 3.00 mm; body densely foveolate.

Proceratium amazonicum belongs to the P. micrommatum clade as defined by Baroni Urbani and de Andrade (2003). In the same phylogeny, a small group inside of the P. micrommatum clade is formed by the species Proceratium brasiliense, Proceratium catio, Proceratium colombicum and Proceratium ecuadoriense. All these species have the propodeal tumulus covered with short hairs on the dorsum, as does P. amazonicum. Proceratium amazonicum can be easily distinguished from any other species in P. micrommatum clade, by the combination of total length over 3.00 mm, with a tumulus on propodeum and has a completely sculptured gaster. Proceratium catio and P. brasiliense have sculpture limited to the middle of the gaster, while in P. amazonicum the gaster is completely sculptured. Proceratium colombicum is smaller (TL < 2.90 mm in P. colombicum, 3.39 mm in P. amazonicum). Proceratium ecuadoriense also has a completely sculptured gaster, but the propodeal tumuli are broad and low in P. ecuadoriense, while in P. amazonicum they are narrow and high. Proceratium colombicum appears as basal to P. brasiliense and P. catio (or sister to P. ecuadoriense) and differs from both, in the worker, by the following set of characters: head, mesosoma, petiole and postpetiole covered by dense granulation instead of granulate-rugulose foveolate, and first gastral tergite entirely densely granulate instead of densely granulate after the curvature only (Baroni Urbani & de Andrade, 2003). Proceratium ecuadoriense appears as the basal species of a small clade containing three additional species: P. brasiliense, P. catio and P. colombicum, but differs from these three taxa by the following two characteristics in the worker: broader and lower propodeal tumulus and deeper integumental sculpture. Proceratium micrommatum specimens from Peru have a transverse carina on the declivous face of the propodeum and the anterior border of the petiole concave. The declivitous face of the propodeum presented some variations in the species, which can be superficially marginate or marked, sometimes dentate (lateral margin of the declivity). Considering the P. micrommatum characteristics, the species can be easily confused with Proceratium mexicanum, but the latter species has the propodeal carina strongly impressed.

Distribution based on Regional Taxon Lists
Neotropical Region: Brazil.

Nomenclature

 *  amazonicum. Proceratium amazonicum Fernandes, Delabie & Fernández, 2019: 552, figs. 1, 2 (w.) BRAZIL.

Worker
Holotype measurements: SL: 0.52, HW: 0.70, HL: 0.79, EL: 0.03, WL: 0.86, PW: 0.48, PtL: 0.28, PtH: 0.26, PtW: 0.28, LT3: 0.35, LT4: 0.60, LS4: 0.18, GL: 0.97, TL: 3.39, CI: 88, OI: 4, SI: 65, IGR: 0.30, ASI: 171, DPeI: 100.

Head longer than broad; sides slightly narrower anteriorly than posteriorly. Vertex in full face view convex. Clypeus recognizable as small triangular or subtriangular tooth between antennal sockets. Frontal carinae close to each other, not covering antennal insertions. Lateral expansions of the frontal carinae relatively narrow, raised and diverging posteriorly. Frontal triangle elevated. Genal carinae strongly marked. Sulcus between genal carinae and gular area impressed. Eyes present, composed of 6−7 convex facets slightly below midline of head. Scapes thicker in distal half and far short of vertexal margin. First funicular joint 1/4 longer than broad. Mandible with 4 denticles including the apical tooth.

Mesosoma slightly elongate. Promesopleural and mesometapleural sutures weakly impressed. Propodeum with elevated tumosity (tumulus) on apex, before the declivity. Declivous face of propodeum flat, sides crenulate and concave close to propodeal lobes. Propodeal lobe semitransparent. Propodeal spiracle tumuliform. Petiole slightly longer than broad, with sides subparallel in anterior third and convex posteriorly in dorsal view. Anterior border of petiole straight. In lateral, view of the basal area of petiole slightly smaller than the apex. Ventral process of petiole triangular, semitransparent and sharply pointed. Abdominal segment III (G1 tergite) slightly shorter than 1/3 length of abdominal segment IV (G2 tergite), in lateral view. Abdominal segment III (G1 sternite) with ventral carina, close to anterior border. Abdominal segment IV (G2 sternite), ventrally with marked subround convex projection. Abdominal segment IV (sternite) slightly convex. Constriction between abdominal segments III and IV strongly impressed. Abdominal sternite III very short medially, carinate and protruding anteriorly on sides.

Mid tibiae without pectinate spur. Spurs of fore legs without basal spine. Fore basitarsi longer than mid and hind ones. Pretarsal claws simple. Arolia small.

Sculpture. Head, mesosoma, petiole and gaster densely foveolate. Legs foveolate.

Body covered by hairs of three main types: (1) short, dense, subdecumbent on whole body, very dense on dorsal face of propodeum tumulus, sparse and erect on funicular joints; (2) long, erect or suberect on petiole and on abdominal segment III (G1 sternite, lateral view); sparse on whole body, absent from tumulus of basal face of propodeum and on antennae. Appressed, short and sparse hairs present on head.

Colour ferrugineous-brown with slightly lighter antennae and legs.

Etymology
“amazonicum” is a neologism indicating the provenance of this species from the Amazon (Rondônia state).