Aretidris, David Emmanuel M. GENERAL, 2015

David Emmanuel M. GENERAL, 2015, Aretidris, a new genus of ants (Hymenoptera: Formicidae: Myrmicinae) from the mountains of Luzon Island, Philippines, Myrmecological News 21, pp. 131-136 : 132

Aretidris gen.n.

Type species: Aretidris buenaventei sp.n.

Diagnosis of worker: Palp formula: 3, 2. Antennae 12 - segmented (including antennal scape) with distinct 3 -segmented club. Spur formula: 0, 0. Antennal scrobe absent. In full face view, gena bounded laterally by a longitudinal ridge that runs from dorsal edge of eye to mandibular insertion and is noticeably thickened anteriorly. In full face view, labrum visible below the anterior clypeal margin, even when mouthparts are fully withdrawn into the head. Mandibles with a long narrow basal stem such that a large gap exists between the basal margin of the mandible and the anterior clypeal margin; masticatory margin with a row of 14 small teeth or denticles. In lateral view, promesonotum strongly convex. Entire length of anterior margin of katepisternum produced into a thickened flange, obscuring the posterior margin of procoxa. Metanotal groove strongly impressed. Propodeum convex with a denticle at the junction between the propodeal dorsum and declivity. Petiole sessile. Protuberance or tooth present above and anterior to petiolar spiracle. Petiole slightly larger than postpetiole. Sting long and functional.

Description of worker: Palp formula: 3, 2. Antennae 12 -segmented (including antennal scape) with distinct 3 - segmented club. Antennal scrobe absent. Antennal scape weakly incrassate, reaching beyond the posterior margin of head by at least the thickness of the distal part of scape. In full face view ( Figs. 4, 10), gena with a longitudinal ridge that runs from dorsal edge of eye to mandibular insertion and is noticeably thickened anteriorly. Gena reticulate. Frontal lobes longitudinally striate. Frontal carina short, ending at about mid-length of eye. Clypeus bicarinate; median part narrowly inserted between frontal lobes; anterior margin simple, almost straight, and without an isolated median seta. Labrum visible below anterior clypeal margin, even when mouthparts are fully withdrawn into the head. Mandible smooth, with a long narrowed base such that a large gap exists between the basal margin of the mandible and the anterior clypeal margin, and with 14 small teeth or denticles; apical and subapical teeth largest and the rest diminishing in size posteriad. Posterior margin of head strongly convex. Lateral margin of head converging anteriorly. Eyes located laterally on the head just anterior of the mid-length, and convex, breaking the lateral margin of head. In lateral view, mandibles bent downward and convex, separated by a prominently impressed metanotal groove. Entire length of anterior margin of katepisternum produced into a thickened flange, obscuring the posterior margin of procoxa. Denticle present where propodeal dorsum meets propodeal declivity. Propodeal spiracle circular, located at least one diameter from edge of declivity. Metapleural gland orifice circular, directed posteriorly (best observed in oblique posterior view), without guard hairs, located at the apex of the propodeal lobe; gland bulla small. Longitudinal ruga present above metapleural gland orifice. Petiole sessile, slightly larger than postpetiole; spiracle below base of anterior face; a protuberance or tooth above and anterior to petiolar spiracle; node rounded, junction of convex petiolar dorsum with anterior and posterior faces indistinct; subpetiolar process absent. Postpetiole slightly flattened dorsally, dorsum forming rounded angles with anterior and posterior faces; subpostpetiolar process present as a low rounded lobe in anterior half of sternite, its anterior margin broadly emarginate in ventral view. First gastral tergite large, about half the total length of gaster. Mesotibial and metatibial spurs absent. Pilosity present as mostly long erect or suberect hairs; shorter erect hairs on coxae; erect hairs on gaster sparse. Color reddish-orange to brown, gaster and appendages lighter; antennal club lighter in color than rest of flagellum and scape.

Queen and male castes: Unknown.

Bionomics: These ants nest in rotten logs and forage individually in the leaf litter during the day. They occur at elevations greater than 900 m a.s.l. on the island of Luzon.

Etymology: Areté (ἀρετή, Ancient Greek, excellence) + idris (ἴδρισ, Greek, ant) (WHEELER 1956). Coincidentally, arête (French, ridge) also fits the fact that A. clousei sp.n. was collected on a low ridge bordering a mountain lake.

Comparative notes: Aretidris is unique among ant genera, with a combination of narrow-based mandibles with a denticulate masticatory margin, gena with a ridge running from the dorsal edge of the eye to the mandibular insertion, palp formula 3: 2, convex propodeum armed with a denticle, metapleural gland orifice at the apex of the propodeal lobe, and a protuberance over the petiolar spiracle.

This genus shares some similar characters, e.g., bicarinate median clypeus, with Lordomyrma EMERY, 1897. However, Aretidris has narrow-based mandibles, a genal ridge, and a convex propodeum, all characters absent in Lordomyrma as currently defined. Lordomyrma , moreover, has an antennal scrobe (present but poorly developed in L. furcifera EMERY, 1897, L. infundibuli DONISTHORPE, 1940, and L. crawleyi MENOZZI, 1923), long frontal carina, and propodeal spines, all characters absent in Aretidris (see TAYLOR 2009, 2012). LUCKY & SARNAT ( 2010) found that Aretidris is sister to Lordomyrma, essentially disproving Bolton's hunch about the identity of " Lordomyrma spPH01". WARD & al. (2015) improved the resolution of the phylogenetic relationship of these two genera and recovered them in separate subclades within the newly expanded myrmicine tribe Crematogastrini FOREL, 1893.

Aretidris would have been included in the old sense of the myrmicine tribe Stenammini ASHMEAD, 1905 (BOL- TON 2003). Although BOLTON (2003) established well the morphological diagnosis of Stenammini , WARD & al.

(2015) found many erstwhile stenammine genera distributed throughout the Crematogastrini clade. WARD & al. (2015) thus transferred fifteen extant genera out of the Stenammini into the Crematogastrini . Now included in the Crematogastrini are all the genera under consideration in this paper, namely, Aretidris (= Myrmicine Genus # 26 PH02 sensu WARD & al. (2015 )), Lordomyrma , Vollenhovia MAYR, 1865, Romblonella WHEELER, 1935, Calyptomyrmex EMERY, 1887, Lasiomyrma TERAYAMA & YA- MANE, 2000 and Indomyrma BROWN, 1986.

WARD & al. (2015) were unable to sequence Lasiomyrma and Indomyrma , two endemic Asian genera. Neither genus is morphologically similar to Aretidris .

Lasiomyrma has an anterior median clypeus produced into an obtuse angle, 11 -segmented antenna, elongate-triangular mandibles that usually close tightly with anterior clypeal margin (line drawing of frontal head shows a gap in L. gracilinoda TERAYAMA & YAMANE, 2000), flat dorsum of promesonotum and propodeum, propodeal spines present, and a pedunculate petiole (TERAYAMA & YAMANE 2000). In contrast, Aretidris has an entire anterior clypeal margin, 12 -segmented antenna, narrow-based triangular mandibles that always close with a gap between the mandibular basal margin and the anterior clypeal margin, convex dorsum of promesonotum and propodeum, propodeal armament reduced to denticles, and a sessile petiole.

Indomyrma has reduced eyes with a total of less than 12 ommatidia, an antennal scrobe, albeit weakly developed, bounded dorsally by a distinct frontal carina, median clypeal margin expanded as a notched convex apron that barely covers basal borders of completely closed mandibles, flat dorsum of promesonotum and propodeum, erect hairs in bilateral positions on head, mesosoma, petiole and pospetiole, propodeal spines present, and a pedunculate petiole ( BROWN 1986). In contrast, Aretidris has larger eyes with about eight ommatidia in its longest axis, no antennal scrobe, a short frontal carina, entire median clypeal margin without an apron, strongly convex dorsum of promesonotum and propodeum, erect hairs on head, mesosoma, petiole and postpetiole abundant but not in bilateral positions, propodeal armament reduced to denticles, and a sessile petiole.

WARD & al. (2015) found Aretidris (as Myrmicine Genus # 26 PH 02) to be a sister taxon to the genus Vollenhovia in the Crematogastrini . These two genera are not particularly similar morphologically, sharing only a couple of petiolar features: a protuberance over the petiolar spiracle (also found in Gauromyrmex MENOZZI, 1933 and Romblonella ) and a lack of a petiolar peduncle. That Aretidris and Vollenhovia together are sister to Calyptomyrmex is even more unexpected and problematic. I can find no morphological similarities between Aretidris and Calyptomyrmex .

Aretidris is already included in the myrmicine generic key of GENERAL & ALPERT (2012), as "Unnamed Genus PH03". Only a simple substitution of the name is necessary to key it out among the ant genera of the Philippines.

Key to workers