Echinopla rugosa

Heterick & Kitching (2022) collected this species in the canopy of a lowland dipterocarp forest in Brunei.

Identification
Zettel & Laciny (2017) - A member of the Echinopla serrata group. Worker: Predominantly black, very small, stout species, TL = 4.2 mm. Surface polyporous (Figs. 5–7), dorsal margins of mesosoma with sharp tubercles. Head wider than long (CI = 111). Mesosoma (Fig. 7) roughly one third longer than pronotal width (MI 129), with sharp and deep mesometanotal suture. Pronotum hardly narrower than head, if eyes excluded. Propodeum shorter than promesonotum. Petiole dentate, with three sharp teeth laterally below lateral spine, dorsally with row of six teeth and pair of minute denticles on lateral spine. Pores on gaster tergite 1 about of same size as on dorsum of head and mesosoma (Fig. 7), their distances about as large as their diameters, in most cases slightly smaller; on disk subcumbent pilosity developed. Standing setae on dorsal surface of trunk, on legs and scape short. Setae on tibia sparse and short, not surpassing base of distally following setae.

Echinopla rugosa belongs to the E. serrata group of Xu & Zhou (2015). Its small and stout body relates it to three other species distributed in the region, i.e. Echinopla madli, Echinopla wardi, and Echinopla brevisetosa. The short setae on scapes and tibiae are similar to Echinopla brevisetosa from the Philippines, whereas the more widely spaced pores on gaster tergite 1 resemble the sculpture of Echinopla wardi.

Distribution based on Regional Taxon Lists
Indo-Australian Region: Borneo, Brunei Darussalam, Indonesia, Malaysia, Singapore.

Nomenclature

 *  rugosa. Echinopla rugosa André, 1892b: 47 (w.) BORNEO.

Taxonomic Notes
Zettel & Laciny (2017) - The species identity of E. rugosa André, 1892 was enigmatic. It was describedby a single specimen without naming the type locality. Only the title of André's (1892) publication suggests that it originates from Borneo and was collected by Maurice Chaper. Although André's (1892) original description of E. rugosa provides many details, it does not yield enough characters to separate the species clearly from some other species recently described from West Malaysia, Borneo, and the Philippines (Zettel & Laciny 2015), except for its bronze shimmer. The type of E. rugosa was considered to be lost, as it was not found in the Muséum National d'Histoire Naturelle in Paris nor in other European museums in the course of the AntWeb Project (Brian Fisher, pers. communication).

During a research visit of the senior author in the Museo Civico di Storia Naturale Giacomo Doria, Genova, Italy, the cited specimen, which was suspected to be the holotype, was found in Carlo Emery's collection. The specimen bears the locality "Banguey", which is Pulau Banggi, a small island near the northern tip of Borneo. The way of mounting with the specimen glued on a square card board resembles that of other type specimens of the species newly described by André (1892): Gesomyrmex chaperi, Dimorphomyrmex janeti, Tapinoma flavidum, and Crematogaster biformis (see illustrations in AntWeb 2016).

When comparing the specimen with the original description there is almost perfect agreement. Only the bronze shimmer mentioned in the original description is not recognizable, except for some faint reflexions on the legs. It might have faded due to the age of the specimen (see also notes for E. senilis below). In addition, the pores on gaster tergite 1 are not more superficial ("plus superficielle"), but more widely spaced than on the mesosoma, but this could be an inaccuracy in the description.

We could not find an itinerary of the Borneo expedition of Maurice Armand Chaper (1834–1896) or any proof that he ever reached Pulau Banggi. André (1892) does not provide any locality names, but we have reported (Laciny & al. 2015) an ant specimen (Diacamma magdalenae Laciny, Pal & Zettel, 2015) collected by Chaper in "Ban du Kapouas", West Kalimantan, which might be the worker mentioned by André (1892) under the name Diacamma intricatum. We have studied two other zoological reports (Drouet & Chaper 1892, Mocquard 1892) which deal with Chaper's material; both mention only localities from Borneo's western part.

The most plausible explanation is that André (1892) included a specimen in his list that was not collected by Chaper, and that the specimen at hand is the holotype. To stabilize the species identity in this rather difficult species complex, a type is required. As no other specimen exists which could be the type, we suggest that taxonomists follow our interpretation that the MCSN specimen is the holotype, or in the case of disagreement, to consider this specimen as a neotype.

Description
Measurements of holotype worker: TL 4.24; HW1 1.16; HW2 1.07; HL 1.04; EL 0.24; SL 1.00; SW 0.14; HaL 0.12; PML 0.76; PMW 1.04; PpL 0.59; PpW 0.98; PH 0.46; PL 0.38; PW 1.03; GL 1.30; GW 1.24. Indices: CI 111; SI 86; MI 129.

Structures: Head (Fig. 5) wider than long, subtrapezoidal, with slightly convex sides; dorsally and laterally polyporous, with closely set pores, posterolaterally with a few hardly recognizable tubercles, matt. Compound eye relatively small, moderately protruding, positioned slightly behind middle of head. Frons with weak median carina in anterior half; frontal lobes chiefly horizontally orientated, completely covering antennal fossae in dorsal aspect, maximum distance of margins at mid-length, greater than half of HW2. Clypeus with weak median carina only at base, anterior margin weakly convex. Mandibles striate, masticatory margin with five teeth. Antennal scape moderately long, weakly s-curved, steadily widened from base to apex; antennomeres 8–10 as wide as long.

Mesosoma stout, length only 1.3 times pronotum width; propodeum shorter than promesonotum. Surface polyporous, with closely set pores, dorsal margins with sharp tubercles. Pronotum with strongly developed angles, slightly narrower than head excluding eyes. Promesonotal suture absent. Mesometanotal suture sharp, narrow and deep. In dorsal aspect mesosoma with waist-like incision in front of propodeum. Legs moderately long; femora not much widened.

Petiole wide and stout, subtriangular in lateral, strongly transverse in dorsal aspect; surface structure as on mesosoma; sharp dorsal crest bearing six sharp teeth medially and one pair of small denticles laterally; lateral spines prominent, right one bifid; below lateral spine with three sharp teeth. Gaster tergite 1 slightly longer than wide, strongly convex, and completely covering the following tergites; hind margin moderately convex, finely serrate; surface polyporous, interspaces smooth and shiny; distances of pores subequal to their diameters, mostly slightly smaller.

Pilosity: Head (except ventral surface), mesosoma, petiole, and gaster tergite 1 with dense, appressed white pilosity and relatively short white standing setae. Standing setae on anterior part of gaster tergite 1 longer than on other parts. White standing setae on scape shorter than scape width. Legs with fine appressed pilosity. Femora with very few (0–3) long standing setae on flexor side. Standing setae on tibiae oblique, sparse and short, their apices not reaching bases of following setae.

Colour: Trunk black, without metallic shimmer, appearing grey by whitish pilosity. Antenna with black scape and base of funiculus, distal part pale brown. Mandible basally black, distally brown; other mouthparts yellowish. Legs chiefly dark brown with a light bronze shimmer; apex of tarsi pale brown.

References based on Global Ant Biodiversity Informatics

 * André E. 1892. Voyage de M. Chaper à Bornéo. Catalogue des fourmis et description des espèces nouvelles. Mém. Soc. Zool. Fr. 5: 46-55.
 * Chapman, J. W., and Capco, S. R. 1951. Check list of the ants (Hymenoptera: Formicidae) of Asia. Monogr. Inst. Sci. Technol. Manila 1: 1-327
 * Emery C. 1886. Saggio di un catalogo sistematico dei generi Camponotus, Polyrhachis e affini. Memorie della Reale Accademia delle Scienze dell'Istituto di Bologna 5: 363-382
 * Pfeiffer M.; Mezger, D.; Hosoishi, S.; Bakhtiar, E. Y.; Kohout, R. J. 2011. The Formicidae of Borneo (Insecta: Hymenoptera): a preliminary species list. Asian Myrmecology 4:9-58
 * Stitz H. 1938. Neue Ameisen aus dem indo-malayischen Gebiet. Sitzungsber. Ges. Naturforsch. Freunde Berl. 1938: 99-122.
 * Viehmeyer H. 1916. Ameisen von Singapore. Beobachtet und gesammelt von H. Overbeck. Archiv für Naturgeschichte (A)81(8):108-168.
 * Zettel H. and A. Laciny. 2017. Further additions to the taxonomy and distribution of the ant genus Echinopla (Insecta: Hymenoptera: Formicidae). Ann. Naturhist. Mus. Wien B. 119: 7-16.