Ooceraea quadridentata

The type material was collected in Nam Kar Nature Reserve (Dak Lak Province, Vietnam) by destroying a partly rotten, hard tree stump in a highly disturbed and bamboo-mixed evergreen forest patch near the forest edge. The colony fragment contained 16 workers but lacked queens, males and immatures.

Identification
Yamada et al. (2018) - Ooceraea quadridentata is easily and precisely distinguished from the other described congeners by its propodeum armed with two pairs of denticles. Furthermore, the number of antennal segments is also one of the useful species-level diagnostic characters in the genus. Nine-segmented antenna is seen in eight species, including Ooceraea quadridentata.

Distribution based on Regional Taxon Lists
Oriental Region: Vietnam.

Nomenclature

 *  quadridentata. Ooceraea quadridentata Yamada, Luong & Eguchi, 2018: 18, figs. 1-11 (w.) VIETNAM.

Worker
Holotype: HL, 0.89 mm; HW, 0.74 mm; SL, 0.49 mm; ML, 1.13 mm; MW, 0.54 mm; PL, 0.41 mm; PH, 0.48 mm; PW, 0.38 mm; PPL, 0.42 mm; PPH, 0.40 mm; PPW, 0.40 mm; CI, 83; SI, 66; PI1, 85; PI2, 93; PPI1, 105; PPI2, 95; WI, 106. Paratypes (n = 7): HL, 0.82–0.89 mm; HW, 0.70–0.75 mm; SL, 0.45–0.50 mm; ML, 1.03–1.13 mm; MW, 0.52–0.58 mm; PL, 0.38–0.41 mm; PH, 0.44–0.50 mm; PW, 0.33–0.39 mm; PPL, 0.38–0.45 mm; PPH, 0.37–0.43 mm; PPW, 0.38–0.45 mm; CI, 84–88; SI, 62–65; PI1, 82–86; PI2, 88–95; PPI1, 99–107; PPI2, 93–103; WI, 106–118

Size and color. Relatively large (HW, 0.82–0.89 mm; ML, 1.03–1.13 mm). Body dark reddish brown; antennae and legs paler.

Structure. Cranium in full-face view subrectangular, a little longer than wide (CI, 83–88); lateral margin weakly convex; posterior margin concave medially. Parafrontal ridge prominently produced anteriad in dorsal view. Torulo-posttorular complex relatively broad, with maximum width between outer edges of the lobes in fullface view approximately as long as major axis of antennal socket. Ventrolateral margin of cranium in lateral view weakly concave. Compound eye and ocelli completely absent. Antenna 11-segmented with enlarged apical segment XI which is almost as long as segments V–X combined; antennal segments III very short; III-X gradually become longer apically. Antennal scape when folded back just reaching the midlength of cranium in full-face view. Area encircling antennal socket which is delimited by torulo-posttorular complex and parafrontal ridge strongly depressed. Masticatory margin of mandible with a series of inconspicuous small teeth. Maxillary palps 3-segmented, with lateroapical part of segment II strongly produced. Labial palps 2-segmented. Pronotal flange separated from collar by distinct ridge. Posterior face of propodeum margined by conspicuous lateral ridges each of which is armed with two conspicuous denticles; in lateral view, the anterior pair of the denticles large subtriangular but blunt apically, and the posterior pair small digitiform. Petiole in lateral view much higher than long when including subpetiolar process (PI1, 82–86); dorsal margin weakly convex. Petiole in dorsal view subrectangular, a little longer than wide (PI2, 88-95); lateral margins slightly convex. Subpetiolar process in lateral view rounded-lobate with conspicuous posteroventral projection (white arrow in Fig. 9). Postpetiole in lateral view subrectangular, around as long as high (PPI1, 99–107); dorsal margin weakly convex. Postpetiole in dorsal view subtrapezoidal, wider posteriorly, almost as long as wide (PPI2, 93–103), a little wider than petiole (WI, 106–118); lateral margins weakly convex. Postpetiolar sternite in lateral view low, not raised ventrad; ventral margin almost straight; anterovental corner strongly angulate.

Sculpture. Dorsal and lateral faces of cranium deeply foveolate-reticulate; foveae relatively large (ca. 0.03– 0.06 mm). Area encircling antennal socket, which is delimited by torulo-posttorular complex and parafrontal ridge shagreened without foveae. Outer face of mandible coarsely rugose in basal part, and smooth in apical part. Pronotal flange partially shagreened with several foveae. Dorsal and lateral faces of mesosoma foveolate; foveae shallower and more sparsely distributed than those of cranium. Posterior face of propodeum smooth. Legs roughly shagreened. Doral and lateral faces of petiolar tergite and postpetiole coarsely and shallowly foveolate-reticulate. Abdominal tergite and sternite IV densely foveolate; foveae somewhat smaller than those of cranium and mesosoma. Pilosity. Body entirely densely covered with flagelliform decumbent or standing hairs.

Type Material
Holotype, worker, colony no. AKY11x17-114, Vietnam, Dak Lak Province, Nam Kar Nature Reserve, N 12.277°, E 108.094°, ca. 545 m alt., 11.x.2017, A. Yamada leg. (deposited in ). Paratypes, 11 workers from the same colony as the holotype (AKYC,, , , ).

Etymology
The specific epithet, quadridentata, describes the two pairs of (i.e., four) conspicuous denticles on the propodeum that is unique to this species.