Acanthognathus rudis

Distribution based on Regional Taxon Lists
Neotropical Region: Brazil, Paraguay.

Biology
Nests in rotten wood.

Castes
Ergatoid queens occur as well as winged queens (Silva & Brandao 2014)

Nomenclature

 *  rudis. Acanthognathus rudis Brown & Kempf, 1969: 100, figs. 1, 2, 4-10 (w.q.m.) BRAZIL. Wheeler, G.C. & Wheeler, J. 1969: 110 (l.). See also: Dietz & Brandão, 1993: 683; Bolton, 2000: 17.

Worker
Holotype. TL 4.2, HL 0.93, H\V 0.65 (CI 70), ML 0.68 (MI 73), WL 0.86, petiole L in dorsal view 0.55, postpetiole L 0.20 (W 0.20), gaster L 0.97, greatest diameter of compound eye 0.3, scape L (chord to basal collar) 0.76 mm.

This species is so well known (under the name ocellatus) that Figs. 1, 2, and 4, and the measurements and indices, plus mention of  a few outstanding features, should suffice to characterize it. Note the rather V-like outline of the posterior excision of the head. Head slightly more depressed, less convex above, than in  A. ocellatus. The outstanding trait is the fine, nearly opaque, densely rugulose­ punctulate sculpture  of  head  and  truncus. Among the rugules are crowded numerous small piligerous fossae, especially on the dorsum of the head, but these are clearly visible only in certain lights. Sides of truncus finely punctulate-rugulose, except for the lowest part of the mesothorax, which is smooth and shining. The hairs are abun­dant, particularly on head and promesonotum, but also present on nodes, short and inclined, slender but blunt, often feebly flattened or clavate toward their apices, those on the head directed anteriad.

Pilosity otherwise as described for the genus.

Humeral angles obtuse, not strongly projecting. Propodeal teeth diverging, very feebly curved as seen from above.

The mandibles lack preapical armament, and there is not even a distinct welt at the site of the trigger hair, though a formation extending internally to the base of the hair can be seen within the transparent cuticle of the inner mandibula margin.

Petiole with a low, rounded node, the lower anterior slope with a low median carina; node about 0.22 mm long and 0.r 8 mm wide; postpetiole subglobular. Petiole and  postpetiole  densely and finely reticulo-punctulate and opaque, except for the almost completely smooth, shining nodal summits. Color light reddish ferruginous ; nodes and gaster yellowish fer­ruginous; but the gaster with the middle third shading into a broad brownish-red  transverse  band ; appendages  yellow  to  straw.

Paratype variation is slight on the whole. Workers from Boraceia, S. Paulo State, have the upper as well as lower mesopleura largely smooth  and  shining. Color varies from light to medium ferruginous.

Queen
Measurements of a queen from the type locality are given in Table I. Her distinguishing specific characters correspond in the usual way to those of the worker. Mesonotum with crowded, slightly vermiculate longitudinal rugulae, interspersed with small fossae. Pronotum and propodeum transversely rugulose. Mesopleura with the upper half rugulose or smooth; lower half mostly smooth and shining.

Male
from the type nest series: TL 2.8, HL 0.52, HW without eyes 0.45, with eyes 0.54, L antenna 2.0, ML 0.05, WL 0.90, L forewing 2.55  mm.

Smooth and shining, with small punctures abundant on head, a few rugae around the antennal insertions. Mesonotum finely and indistinctly longitudinally striolate-punctulate, sericeous-opaque. Color brown to piceous, head darkest (specimens may not be fully colored). Legs and mouthparts yellowish-tan.