Aretidris

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

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scientific name

Aretidris
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gen.n.

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 In full face view, labrum visible below the anterior clypeal margin, even when mouthparts are fully withdrawn into the head.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.

Queen and male castes: Unknown.

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

– Head and mesosoma mostly smooth; erect hairs st sparsely distributed on head and mesosoma; 1 gastral tergite extremely large, accounting for most of the length of gaster; body smaller ( HW <0.84). .......................................... A. clousei  sp.n.