Eurhopalothrix depressa

The type material was collected from Winkler samples.

Identification
Ketterl et al (2004) - E. depressa belongs to the Eurhopalothrix bolaui species group (Brown & Kempf, 1960) defined by a dentate propodeum and specialized erected hairs. It can be separated from all other Eurhopalothrix by the following characters: a distinct transverse ridge dividing the head in a lower anterior and a higher posterior part. Mesonotum in front of the metanotal groove with a median longitudinal prominent carina. On the head remarkable shallow depressions, one above each eye and two in the middle of the vertex at either side of the central carina. The number of 16 modified hairs on the head is unique amongst New World species. The typical pit-like foveae at the base of the larger specialised hairs on the head, mesosoma, petiole and postpetiole are similar to those in Eurhopalothrix speciosa. From the similar sized Eurhopalothrix gravis it can be separated by the less angular shaped head corners and the outermost specialised hair of the lower row on the head situated above the eye (in E. gravis it is at the base of the eye). The frontal margin of the clypeus is strikingly concave (in E. gravis it is nearly straight), the overall pilosity scarcer and the apical part of the specialised hairs of the

Longino (2013) - This is a highly distinctive species, one of only two New World species with a transverse ridge on the frons, the other species being Eurhopalothrix cimu from Cuba. Eurhopalothrix depressa has 16 erect spatulate setae on the face; E. cimu has none.

Distribution
Brazil (Rio Grande du Sul, Sao Paulo)

Distribution based on Regional Taxon Lists
Neotropical Region: Brazil.

Nomenclature

 *  depressa. Eurhopalothrix depressa Ketterl, Verhaag & Dietz, 2004: 45, figs. 23 (w.q.) BRAZIL.

Worker
TL 3.52–3.60mm, ML 0.13–0.15mm, HL 0.85–0.90mm, HW 0.83–0.88mm (CI 100–102), ED 0.07–0.11mm, SL 0.49–0.54mm, SLL 0.15–0.17mm, SLL/SL 0.30–0.31mm, PW 0.42–0.48mm, AL 0.80–0.84 mm, HFL 0.59–0.61mm.

Holotype. Whole body opaque and densely punctuate-granulated except for the gaster, vertex and anterior part of pronotum which are markedly foveolate. Head (except brownish scrobes), first gastral tergite and sternites dark brown. Rest of body slightly lighter brown. Pilosity and erect hairs yellowish white.

Head 1.02 times longer than broad, divided in a lower anterior and a higher posterior part by a transverse arc-like elevation that ends beneath the eyes. Above the eyes and in the median part of the vertex with broad but shallow depressions. Clypeus 1.35 times broader than long. Anterior clypeal margin with a broad median impression. Eyes globular, consisting of about 25 ommatidia. Antennal scrobes finely punctuate, apical part at level of antennal insertion more coarsely punctuate. Inferior border of antennal scrobe translucent. Scape greatly expanded anteriad (see measurement of SLL). Outer margin of scape translucent. Apical segment of flagellum 2.24 X longer than broad.

Promesonotal suture and metanotal groove present, the former only weakly defined, the latter distinct. Mesonotum in front of the metanotal groove with a small, longitudinal, elevated median carina. This carina may be in front and behind connected to other transversally oriented carinae, the whole arrangement thus forming the border of a more or less distinct fovea in which the specialised modified posterior hairs are located. Propodeum relatively short and sloping to the well developed acute propodeal spines, promesonotum and propodeum not forming a continuous curve. Infra-dental lamellae present. Petiole sub-quadrate in dorsal view, with a small subpetiolar process. Postpetiole 1.90 X broader than long.

Moderate to scarce general pilosity on all body parts consisting of simple appressed and subappressed hairs. Femora and tibiae with small spatulate hairs, tibiae apically with one large spatulate hair. Tarsi and metatarsi with spatulate hairs externally, internally with simple setae. Inner sides of scapes with simple hairs, outer sides with many spatulate hairs. Erect clavate to spatulate hairs on head, mesonotum, petiole, postpetiole and gaster. The typical pattern in the bolaui group of 18 specialised hairs on the head is reduced to 16 spatulate hairs representing only two hairs in the middle row. Mesonotum with 4 thick clavate hairs, one of which is broken in the holotype. Petiole with two thick clavate hairs directed backwards. Postpetiole with two outer thick clavate hairs and two inner small clavate hairs, also directed backwards. Modified hairs on head, mesosoma, petiole and postpetiole each surrounded by a pit-like fovea. First gastral tergit with 17 clavate or spatulate hairs arranged in four longitudinal rows of 4–5 hairs each.

Queen
TL 3.75–3.93mm, ML 0.15mm, HL 0.90mm, HW 0.87mm (CI 103), ED 0.13–0.15mm, SL 0.52–0.54 mm, SLL 0.17–0.18 mm, SLL/SL 0.32–0.33mm, PW 0.55–0.57mm, AL 0.98–1.02 mm, HFL 0.64–0.65mm.

Female much like the worker with the caste-specific morphological modifications. Surface of head, pronotum, and prododeum with less marked sculpture. Pilosity less conspicuous than in worker (this is uncommon for the genera of Basicerotini where queen pilosity usually is more conspicuous).

Type Material
Holotype worker from São Francisco de Paula, Rio Grande do Sul, Brazil, Araucaria forest reserve Pró-Mata, in leaf litter of an Araucaria forest (29°30'S 50°10'W), J. Ketterl leg. 3.4.1997 . Paratypes, 2 workers from the type locality ( and ), and 1 worker and 2 queens from Pico da Macela, Cunha, São Paulo State (23°08¢S 44°48¢W), Brazil, A. A. Tavares & R. R. Silva leg. 21./22.4.2001 (MZSP).

Etymology
The species is named because of the remarkable depressions above the eyes and in the median part of the vertex.