Recurvidris nigrans

Nothing is known about the biology of .

Identification
Zettel (2008) - Body chiefly blackish brown, funiculus of antenna and tarsi yellowish. Body surface smooth and shiny. Head broad, HW 0.61-0.65, CI 99-103. Clypeus without distinct carinae. Mandible with four acute teeth on apical margin and one prominent, acute tooth at basal margin. Propodeum dorsally with 1-2 pairs of short decumbent setae, with long, slender, recurved spines, without infradental lamellae between spines and metapleural lobes. Petiole (Fig. 1) with very slender peduncle ventrally bearing a spiniform subpetiolar process; node in lateral view forming an acute angle anteriorly (at insertion of anterior setae).

Recurvidris nigrans meets all morphological criteria of the Recurvidris kemneri group listed by Bolton (1992), i.e., the characteristic dentition of the mandible, the absence of infradental lamellae on the propodeal declivity, and a broad head (range of CI 94-106 in the group, 99-103 in R. nigrans). This species group contains only two further taxa, Recurvidris kemneri from Borneo and Java and Recurvidris proles from Sulawesi. Comparing the key characteristics which distinguish these two species, R. nigrans is more similar to R. proles, because it is relatively large in size, lacks clypeal carinae and bears 1-2 pairs of setae on the propodeal dorsum. The dark body colour of R. nigrans nov.sp. differs from both species (as well as from all other congeners!); R. kemneri is uniformly yellow, R. proles is yellow with brown head and gaster. Further differences between R. nigrans and R. proles are the following: The tooth on the basal margin of the mandible is strongly developed in R. nigrans (almost as large as the forth tooth), but small in R. proles. The dorsum of the propodeum bears short, decumbent setae in R. nigrans, but comparatively long standing setae in R. proles. The subpetiolar process is narrow, relatively long and acute in R. nigrans, but small and triangular in R. proles (for the latter two characteristics see Bolton 1992: fig. 8). Recurvidris sp_phi1 from Camarines Sur in southern Luzon (Alpert et al. 2008) differs from the new species by much smaller size (TL c. 2.1, HW c. 0.4), uniformly yellow colour, and a relatively stout petiolar peduncle in lateral aspect.

On average, R. nigrans is the largest known species of Recurvidris.

Distribution
Negros Island, Philippines.

Distribution based on Regional Taxon Lists
Indo-Australian Region: Philippines.

Nomenclature

 * . Recurvidris nigrans Zettel, 2008: 892, figs. 1-4 (w.) PHILIPPINES (Negros I.).
 * Type-material: holotype worker, 10 paratype workers.
 * Type-locality: holotype Philippines: Negros I., Negros Oriental, Cuernos de Negros, Valencia, Apolong, Casaroro Falls, 28.i.2007, no. 456 (H. Zettel); paratypes with same data but 3-4.iii.2008, no. 513.
 * Type-depositories: USCC (holotype); HSZC, NHMW (paratypes).
 * Status as species: Jaitrong, Tokeeree, et al. 2019: 60 (in key).
 * Distribution: Philippines (Negros).

Worker
Holotype: TL 3.2; HL 0.63; HW 0.65; CI 103; SL 0.57; SI 89; PW 0.35; AL 0.86. Measurements of paratypes (n = 10): TL 2.9-3.2; HL 0.61-0.64; HW 0.61-0.65; CI 99-102; SL 0.56-0.59; SI 89-94; PW 0.34-0.35; AL 0.81-0.86.

Head broad and smooth, lacking sculpture except hair pits, setiferous pits and some rugae near mandible base. Mandible (Fig. 4) smooth and shiny, with some relatively large hair pits, apical margin with four teeth, forth tooth acute, basal margin with one acute tooth almost as large as forth tooth of apical margin. Clypeus (Fig. 4) without paired carinae, but with indistinct paired elongate swellings. Eyes comparatively large, containing 8 ommatidia in longest row. Profile shape of alitrunk, petiole and postpetiole as in image. Alitrunk smooth and polished, with some very fine setiferous pits, only part of mesopleuron with some fine rugae. Promesonotum with 4 pairs of setae plus one median seta posteriorly. Impression behind mesonotum appearing angular in profile. Propodeum comparatively high, dorsal surface with 1-2 pairs of short subcumbent setae in front of spiracle; spines very high, slender, divergent, and in caudal view very narrow (blade-like). Petiole with 2-3 pairs of dorsal setae; peduncle in profile long and very slender, its dorsal outline distinctly concave and ending posteriorly in a sharp angle at insertions of anterior pair of setae (insertions separated from each other by shallow impression), its ventral outline with long, spiniform subpetiolar process; node low. Postpetiole with 3 dorsal pairs and 1 ventrolateral pair of setae, low and with deep helcium, as typical for the genus. Gaster moderately depressed. Petiole, postpetiole, and gaster polished except for very fine setiferous pits. Colour blackish brown, alitrunk, petiole and postpetiole slightly lighter. Scape of antenna brown, funiculus yellowish. Mandibles brown, distally yellowish. Legs dark brown, but tarsi yellowish.

Type Material
Type material: Holotype worker labelled “Philippines: Negros Or., Cuer-\ nos de Negros, Valencia\ Apolong, Casaroro Falls, 28.\ 1.2007, leg. H. Zettel (456), in the Entomological Collection of the University of San Carlos, Cebu City, Philippines. 10 paratype workers labelled “Philippines: Negros Oriental\ Cuernos d.N., Valencia\ Apolong, Casaroro Falls\ 3-4.3.2008, lg. Zettel (513)” in the Natural History Museum Vienna, Austria, and in the author's collection.

Philippines, Negros Island, Negros Oriental Province, Cuernos de Negros Mountains (= Mount Talinis), municipality of Valencia, barangay Apolong, Casaroro Falls; 9° 16' N, 123° 12' E, c. 500-550 m a.s.l. (GPS).

Etymology
The Latin adjective “nigrans” means dark and refers to the dark body colour of the new species that differs from all other hitherto known congeners.