Ooceraea siamensis Jaitrong, Yamane et Wiwatwitaya, 2021

Jaitrong, W., Yamane, Sk. & Wiwatwitaya, D., 2021, A new species and a new record of the ant genus Ooceraea Roger, 1862 (Hymenoptera: Formicidae: Dorylinae) from Thailand, Far Eastern Entomologist 441, pp. 1-10 : 6-9

Ooceraea siamensis Jaitrong, Yamane et Wiwatwitaya , sp. n.

http://zoobank.org/NomenclaturalActs/ 667D9A7E-55F3-49BA-9EF6-B13A269E3DF4

Figs 3 , 4

TYPE MATERIAL. Holotype - worker (THNHM-I-02628, THNHM), Thailand:

Trang Province, Palian District, Ban Nong Malai, near a house, 23.XII 2018, W.

Jaitrong leg., colony no. WJT231218 - 8. Paratypes: twenty-four workers [ SKYC

(THNHM-I-19127 and THNHM-I-19128) and THNHM (THNHM-I-19105 to

THNHM-I-19126)] and 2 dealate queens ( THNHM, THNHM - I - 02626 and THNHM -

I - 19104), same data as holotype.

MEASUREMENTS AND INDICES. Worker (holotype and paratypes, n = 10) :

HL 0.43–0.46, HW 0.33–0.38, SL 0.20–0.23, MW 0.23–0.30, ML 0.50–0.56, PL

0.18–0.21, PH 0.23–0.26, PW 0.20, PPL 0.23–0.25, PPH 0.23–0.26, PPW 0.23–

0.26, CI 77–82, SI 60–61, PI1 75–81, PI2 92–109, PPI1 88–100, PPI2 100–107, WI

117–133. Dealate queen (paratypes, n = 2): HL 0.46–0.50, HW 0.38–0.40, SL 0.21–

0.23, EL 0.08–0.10, MW 0.36–0.40, ML 0.66–0.69, PL 0.20–0.23, PH 0.28–0.30,

PW 0.20, PPL 0.26, PPH 0.23–0.26, PPW 0.30, CI 80˗82, SI 54–61, EI 22–25, PI1

67–82, PI2 86–100, PPI1 99, PPI2 100–106, WI 133–141.

DIAGNOSIS. Worker ( Fig. 3 ). Body small (head width 0.33–0.38 mm), reddish brown (light brown in some paratypes); antenna 9-segmented; propodeal declivity shallowly concave and encircled with distinct rim; dorsal and lateral faces of head,

mesosoma, petiole, postpetiole and abdominal tergite IV (= first gastral tergite)

finely and shallowly foveolate; foveae on first gastral tergite smaller than those of head and mesosoma; propodeal declivity smooth and shiny. Dealate queen ( Fig. 4 ).

Similar to worker in structure, sculpture, coloration and pilosity, but the body size is slightly larger; eye and ocelli are present.

DESCRIPTION. WORKER ( Fig. 3 ). Size and color. Relatively small (HW

0.33–0.38 mm; ML 0.50–0.56 mm). Body reddish brown; mandible dark brown;

legs and antenna yellowish brown.

view; B – body, dorsal view; C – head in full-face view; D – postpetiole and abdominal tergite IV, dorsal view.

Structure. Head in full - face view clearly longer than broad; lateral margin weakly convex; posterior margin concave. Antenna 9 - segmented with enlarged apical segment (IX) which is almost as long as III–VIII combined; scape short, when laid straight back not reaching mid - length of head in full - face view; antennal segment II almost as long as broad; III–V broader than long. Frontal carinae short, narrow and extending less than half length of head, sharply elevated in anterior half, and low and vestigial in posterior half. Parafrontal ridge short, seen in profile its dorsal outline weakly convex anteriorly. Clypeus short with its anterior margin concave.

Compound eye and ocelli completely absent. Mandible triangular, its masticatory margin with a series of inconspicuous small denticles. Mesosoma rather robust,

seen from above broader anteriorly, almost parallel - sided in posterior half; in profile view, promesonotum weakly convex dorsally and sloping gradually to metanotal groove; promesonotal suture absent; mesopleuron not clearly demarcated from metapleuron; mesopleuron clearly demarcated from lateral face of promesonotum by deep groove. Propodeal declivity deeply concave, encircled with a distinct rim except ventrally. Petiole in dorsal view almost as long as broad, almost parallel -

sided; in profile, petiole including subpetiolar process higher than long, its node subrectangular and weakly convex dorsally; s ubpeiolar process in profile rounded -

lobate with conspicuous posteroventral projection. Postpetiole in dorsal view subrectangular, slightly longer than broad and slight broader that petiole; in profile view, postpetiole almost as long as high, its dorsal outline weakly convex;

postpetiolar sternite in profile view low, ventral margin weakly convex;

anteroventrally produced as a blunt angle directed downward and forward.

Abdominal tergite IV (= first gastral tergite) elongate - subrectangular ( Fig. 3D ), in dorsal view, its anterior margin concave and lateral margins weakly convex or almost parallel - sided.

Sculpture. Dorsal and lateral faces of head, mesosoma, petiole, postpetiole and first gastral tergite shallowly and finely foveolate; foveae on first gastral tergite smaller than those of head and mesosoma. Antennal scape and legs micropunctate.

Outer face of mandible punctate, with smooth interspaces.

Pilosity. Body entirely covered with short decumbent and standing hairs.

DEALATE QUEEN ( Fig. 4 ). Similar to the worker in structure, sculpture, coloration and pilosity, with the following conditions that should be noted: body slightly larger (HW 0.38–0.40 in dealate queen; 0.33–0.38 mm in worker); head in full - face view longer than broad; lateral margins weakly convex; posterior margin weakly concave; eye present, with 5–6 ommatidia along the longest axis, located anterior to mid - length of head (absent in worker); ocelli present (absent in worker), median ocellus smaller than lateral ocelli, distance between median ocellus and lateral ocelli shorter than distance between lateral ocelli; mesosoma stout, in profile view its dorsal outline weakly convex; promesonotal suture and metnotal groove distinct;

in dorsal view, pronotum almost as long as mesoscutum; mesoscutum trapezoidal,

almost as long as broad, anterior edge strongly convex while posterior edge straight;

scutellum small, almost as long as broad; metanotum very short; propodeum with straight dorsal outline, slightly longer than scutellum; propodeal junction nearly right - angled, its declivity concave, encircled with a distinct rim except ventrally.

view; B – body, dorsal view; C – head in full-face view; D – postpetiole and abdominal tergite

IV, dorsal view.

REMARKS. Ooceraea siamensis is most similar to O. biroi (see specimen codes

CASENT0916710 and CASENT0907059 on AntWeb, 2021) in having a slender body and 9-segmented antenna. However, O. siamensis can be distinguished from

O. biroi by the following characteristics: 1) postpetiole slightly longer than broad in dorsal view (clearly shorter than broad in O. biroi); 2) foveae on first gastral tergite and sternite denser and coarser (weak in O. biroi); 3) smaller body size (HW 0.33–

0.38 in O. siamensis ; 0.46–0.49 mm in O. biroi).

DISTRIBUTION. Thailand (Trang Province).

HABITAT. The single colony was collected from a fruit orchard near a house,

nesting in soil.

ETYMOLOGY. The specific name is an adjective meaning ‘of Siam’ (a historic name of Thailand).

Figures

Fig. 3. Ooceraea siamensis sp. n., holotype worker (THNHM-I-02628). A – body, lateral

Fig. 4. Ooceraea siamensis sp. n., paratype queen (THNHM-I-02626). A – body, lateral