Odontomachus rixosus F. Smith, 1857

Satria, Rijal, Kurushima, Hiroaki, Herwina, Henny, Yamane, Seiki & Eguchi, Katsuyuki, 2015, The trap-jaw ant genus Odontomachus Latreille (Hymenoptera: Formicidae) from Sumatra, with a new species description, Zootaxa 4048 (1), pp. 1-36 : 21-27

Odontomachus rixosus F. Smith, 1857

( Figs. 11 , 12 , 13 , 17, 18)

Odontomacus rixosus F. Smith, 1857: 64 , worker, type locality: Singapore. Forel, 1900: 58; Viehmeyer, 1916: 116; Crawley, 1924: 388 (q); Karavaiev, 1925: 293; Chapman & Capco, 1951: 45; Wheeler & Wheeler, 1952: 651 (l); Brown, 1976: 163; Imai, Brown et al, 1984: 67 (k). Bolton, 1995: 297; Sorger & Zettel, 2011: 157.

Odontomachus rixosus var. conifera Forel, 1913: 19 , worker, queen, type locality: Indonesia (Java). Chapman & Capco, 1951: 45. Synonymy by Brown, 1976: 105.

Odontomachus rixosus var. obscurior Forel, 1900: 58 , worker, type locality: Myanmar. Viehmeyer, 1916: 116 (q); Chapman & Capco, 1951: 45. Synonymy by Brown, 1976: 105.

Type materials and images examined. Syntype worker of Odontomachus rixosus : syntype (1 worker in BMNH), Singapore [head detached and missing gaster].

Images of the type material of the following species provided in AntWeb v5.17.5 (http://www.antweb.org) were also examined for reconfirming our species recognition: O. rixosus , worker (CASENT0900656); “ O. rixosus conifera ”, worker (CASENT0907432); “ O. rixosus obscurior ”, worker (CASENT0907431).

Non-type materials examined. Indonesia: Sumatra: Aceh: Leuser Ecosystem (ca. 980 m alt.), S. Rijal leg., GK-01-12, 12 workers ( SKYC, RSC); same loc., (ca. 980 m alt.), 19.IX.2012, S. Rijal leg., GK-15-12, 16 workers ( SKYC, RSC); same loc., (ca. 1000 m alt.), 21.IX.2012, S. Rijal leg., GK-42-12, 14 workers ( SKYC, RSC); same loc., (ca. 980 m alt), 19.IX.2012, S. Rijal leg., GK-01-12, 2 workers ( SKYC, RSC); same loc., (ca. 980 m alt.), 20.IX.2012, GK-20-12, 4 workers ( SKYC, RSC); same loc., (ca. 1000 m alt.), 21.IX.2012, S. Rijal leg., GK-40-12, 12 workers, 2 queen ( SKYC, RSC); West Sumatra: Ulu Gadut nr Padang, 27–30.VIII.1985, Sk. Yamane leg., SNS coll., 8 workers ( SKYC); Lubuk Gadang, 21–23.VIII.1985, Sk. Yamane leg., SNS coll., 2 workers ( SKYC); Padang: Ulu Gadut: Pinang-pinang, 22.III.1997, F. Ito leg., F197-385, 3 workers ( SKYC); same loc., 18.II.2007, Sk. Yamane leg., 1 worker ( SKYC); Andalas University’s forest (ca. 200–600 m alt.), 02.IX.2012, S. Rijal leg., PDG-01-12, 6 workers ( SKYC, RSC); same loc., 14.IX.2011, 9 workers ( SKYC, RSC); same loc., 02.VIII.2012, S. Rijal leg., PDG-01-12, 5 workers ( SKYC, RSC); 50 Kota District: Mt. Sago, 06.IX.2012, S. Rijal leg., SAGO-06- 12, 3 workers ( SKYC, RSC); Harau, Gantiang, 10.IX.2012, S. Rijal leg., GTH-01-12, 8 workers, 3 queen ( SKYC, RSC); Tanah Datar District: Barulak, 05.IX.2012, S. Rijal leg., LBT-03-12, 4 wokrkers ( SKYC, RSC); same loc., 07.IX.2012, S. Rijal leg., LBT-11-12, 8 workers ( SKYC, RSC); Solok District: Mt. Talang (general collection), 23– 28.VIII.2012, S. Rijal leg., 4 workers ( SKYC, RSC); Jambi: Merangin: Sungai Manau: Kerinci Seblat N.P., 7.XI.2006, Syaukani leg., SYAU 06-75, 7 workers, 1 queen ( SKYC); Lampung: Sumber Jaya: Bodong Jaya, 16.IX.2007, Sk. Yamane leg., SU07-SKY-149, 4 workers ( SKYC); same loc., 18.IX.2007, Sk. Yamane leg., SU07- SKY-204, 9 workers ( SKYC); W. Lampung: Sumber Jaya (800–900 m alt), 16.IX.2007, Sk. Yamane leg., SU07- SKY-158, 8 workers ( SKYC). Simeulue Island: Luan Boya, 16.IX.2012, S. Rijal leg., LLB-01-12, 29 workers, 2 queens ( SKYC. RSC); Lewak: Alafan, 13.IX.2012, S. Rijal leg., LW-08-12, 17 workers, 4 queens ( SKYC, RSC); same loc., 13.IX.2012, S. Rijal leg., LW-10-12, 11 workers, 1 queen ( SKYC, RSC); E. Simeulue Island: Sinabang, 15.IX.2012, S. Rijal leg., SNB-03-12, 24 workers ( SKYC, RSC); W. Simeulue Island: Babul Makmur, 15.IX.2012, S. Rijal leg., 13 workers, 1 queen ( SKYC, RSC); same loc., same date, BMS-21-12, 10 workers ( SKYC, RSC). Bali: Mendaya: Dusun PK Jelati, 6.V.1998, K. Eguchi leg., EG98-BALI-739, 3 workers ( SKYC); Jembrana District: Pekutatan: Pulukan, 23.X.2012, S. Rijal leg., PKN-01-12, 38 workers, 7 queens ( SKYC, RSC). Mentawai Islands: Siberut Island: Simabuggei, 22.II.2007, Sk. Yamane leg., SU07-SKY-078, 5 workers ( SKYC). Malaysia. Sabah: Poring: Kinabalu (550–600 m alt), 19.III.1995, Sk. Yamane leg., 1 worker ( SKYC); same loc., (450–500 m alt.), 21.XI.1996, K. Eguchi leg., EG96-BOR-269, 1 worker ( SKYC); same loc., (600–700 m alt.), 16.III.1995, Sk. Yamane leg., 2 workers ( SKYC); same loc., (700–800 m alt), Sk. Yamane leg., 5 workers ( SKYC); Poring Hot spring (600 m alt), 20.IX.1993, T. Kikuta leg., 2 workers ( SKYC); Poring (600 m alt), 26.X.1996, T. Kikuta leg., 6.X2606 -(2)Aa, 5 workers ( SKYC), 6X2606 -(8)Ba, 4 workers ( SKYC); Sayap Kinabalu, ca. 1000 m alt., 15.VII.1996, K. Eguchi leg., Eg96-BOR-057, 3 workers, 1 male ( SKYC); same loc., same date, HN-140, 1 workers ( SKYC); same loc., same date, HD-112, 1 worker ( SKYC); same loc., same date, HN-153, 1 worker ( SKYC), same loc., same date, Eg96-BOR-056, 3 workers ( SKYC); same loc., same date, HD-95, 1 worker ( SKYC); same loc., same date, HD-97, 1 worker ( SKYC); same loc., same date, S-17, 1 worker ( SKYC); same loc., same date, HD- 116, 1 worker ( SKYC); same loc., 14.VII.1996, Sk. Yamane leg., 3 workers ( SKYC); same loc., 15.VIII.1996, Sk. Yamane leg., SB96-SKY-5, 1 worker ( SKYC); same loc., 14.VII.1996, Sk. Yamane leg., HC-4, 1 worker ( SKYC); Sg. Kalang, Tenom, 800–1000 m alt., 23.III.1997, Sk. Yamane leg., 1 worker ( SKYC); Danum valley, 2.XI.1996, K. Eguchi leg., Eg96-BOR-125, 6 workers ( SKYC); same loc., 6.XI.1996, K. Eguchi leg., EG96-BOR-203, 3 workers ( SKYC); Tawau hills N. P. HQ., 7-12.VII.1996, Sk. Yamane leg., 1 worker ( SKYC); Tambunan village resort centre, 05.XI.2000, Sk. Yamane leg., SB00-SKY-04, 1 queen ( SKYC); Crocker range N.P., Mahua Waterfall area (ca. 1000 m alt.), 05.XI.2000, B.T. Viet leg., 1 worker ( SKYC); same loc., 04.XI.2000, K. Eguchi leg., Eg00- BOR-110, 1 worker ( SKYC). Sarawak: Bako Nat. Park., 21-22.IV.1993, Sk. Yamane leg., 3 workers ( SKYC); Niah N. P., 9.I.1993, Sk. Yamane leg., 5 workers ( SKYC); Mulu (lowland), 11.XI.1993, Sk. Yamane leg., 2 workers ( SKYC); Miri, Tower region, Lambir N. P., 16.II.1995, Abd. Rahman leg., 1 worker ( SKYC). Malay Peninsula: Selangor: Ulu Gombak, 12.III.1999, F. Ito leg., F199-139, 3 workers ( SKYC); same loc., VII-X.1992, F. Ito leg., 1 worker ( SKYC); same loc., (ca. 250 m alt.), 05.VII.1999, Sk. Yamane leg., 2 workers ( SKYC); Selangor (ca. 250 m alt.), 5.VII.1999, Sk. Yamane leg., 2 workers ( SKYC). Thailand: Chacheongsao: Khao Ang Reu Nai W.S. near Headquarters (secondary forest), 22.VIII.2003, Sk. Yamane leg., TH03-SKY-97, 18 workers, 1 queen ( SKYC). Chanthaburi: Khao Soi Dao W.S. (rainforest), 3.VI.2001, Sk. Yamane leg., TH01-SKY-07, 8 workers, 2 queens ( SKYC); same loc., 20.VII.1997, Sk. Yamane leg., 11 workers ( SKYC); same loc., 19–20.VII.1997, H. Okido leg., 8 workers ( SKYC); Nam Thok Phlio N.P. (300–500 m alt.), 21.IX.2003, Sk Yamane leg., 3 workers ( SKYC). Nakom Ratchasima: Sakaerat lowland forest (DEF), 09.VII.1999, Sk. Yamane leg., 4 workers ( SKYC); Khao Nan N.P., Klong Klai stn., 13.III.2007, Sk. Yamane leg., 2 workers ( SKYC); Khao Nan N.P., Papra stn., 14.III.2007, Sk. Yamane leg., 2 workers ( SKYC). Songkhla: Hatyai, Prince of Songkhla University forest, 17.III.2007, Sk. Yamane leg., TH07-SKY-72, 3 workers ( SKYC); same loc., 17.III.2007, Sk. Yamane leg., TH07-SKY-72, 3 workers ( SKYC); Khao Nam Kang N.P., 25.VII.1997, Sk. Yamane leg., 1 worker ( SKYC); Pattani: Sa i Kho, 25.VIII.1998, Sk. Yamane leg., 1 worker, 1 queen ( SKYC). Trang: Khao Chong (river side), 25.VIII.1998, Sk. Yamane leg., 3 workers ( SKYC). Suratthani: Khlongsane W.S. (evergreen forest), 14.X.2011, W. Jaitrong leg., 1 worker ( SKYC).

Material used for DNA barcoding. Colony BMS-22-12 (RJ20141201-3, accession no. LC056035 ), colony GK-15-12 (RJ20141201-13, LC056036 ), colony GTH-01-12 (RJ20141201-2, LC056038 ), colony LBT-06-12 (RJ20141201-8, LC056039 ), colony LBT-07-12 (RJ20141201-9, LC056040 ), colony LBT-09-12 (RJ20141201-7, LC056041 ), colony LBT-10-12 (RJ20141201-10, LC056042 ), colony SAGO-06-12 (RJ20141201-14, LC056053 ), colony PDG-13-12 (RJ20141114-1, LC056046 ), colony PKN-01-12 (RJ20141114-2, LC056050 ).

Worker measurements and indices. Syntype (n=1, gaster missing): HW 2.10 mm, HL 2.98 mm, SL 2.93 mm, IFLW 0.64 mm, EL 0.36 mm, MDL 1.64 mm, WL 4.00 mm, PTL 0.72 mm, PTH 1.21 mm, CI 70, SI 139, MDI 55, PTHI 168.

Non-types (n=10): HW 1.77–2.19 mm, HL 2.56–3.03 mm, SL 2.56–3.03 mm, IFLW 0.45–0.56 mm, EL 0.31– 0.42 mm, MDL 1.45–1.67 mm, WL 3.35–4.00 mm, PTL 0.57–0.69 mm, PTH 1.09–1.26 mm, CI 64–73, SI 131– 150, MDI 55–57, PTHI 171–196.

Worker description. Relatively small (HL 2.56–3.03 mm, WL 3.35–4.00 mm). Head in full-face view much longer than broad, with posterior margin weakly concave; median furrow on vertex present as dark line; each side of line not swollen; frontal lobes followed by strong frontal carinae which are nearly parallel; minimum distance between margin of ocular ridge and margin of compound eye less than half major axis of compound eye; mandible relatively slender; masticatory margin with 6–10 denticles (7 in a syntype of O. rixosus examined; 7 in a syntype of O. rixosus conifer [ANTWEB CASENT 0907432]; 6 in a syntype of O. rixosus obscurior [ANTWEB CASENT 0907431]); subapical tooth ca. 2.5 times as long as broad, with truncate apex; palp formula 4, 4. Mesosoma in lateral view relatively slender; pronotum including its anteromedian lobe long, in lateral view with anterodorsal slope gentle; mesopleuron without anteroventral ridge, with anterodorsal margin weakly carinate, clearly separated by distinct dorsal carina from mesonotum and metapleuron; propodeum in lateral view with dorsum almost straight and gradually sloping posteriad, and with posterior face steeply sloping; propodeal dorsum without median longitudinal depression. Petiolar node conical, with sharply pointed apical spine; node in lateral view, excluding apical spine with anterior and posterior faces weakly convex; apical spine needle-shaped, less than 1/4 as long as petiolar height, sometimes weakly curved posteriad (but shape variable within species); subpetiolar process anteroposteriorly as long as dorsoventrally high, lobate, directed ventrally. First gastral tergum in lateral view long, with anterior face relatively short and vertical.

Head in full-face view largely smooth and shiny, but with striate area bordered by frontal carinae and ocular ridges; frontal lobe with almost smooth and shiny; extraocular furrow faintly striate; median part of vertex along median furrow smooth and shiny or sometimes with rough texture; lateral face and venter of head smooth and shiny; median disc of clypeus smooth and shiny. Pronotum in dorsal view finely concentrically striate (but sculpture variable within species); mesonotum finely striate transversely; mesopleuron largely smooth and shiny, with anterior 1/3 and posteriormost parts finely striate; metapleuron and propodeum with transverse striation which is a little sparser and stronger than on pronotum and mesonotum. Petiolar node largely smooth and shiny, but with its basal area faintly striate.

Vertex with a pair of long erect setae; frontal lobe with erect seta; pronotal disc without long erect setae; 1st gastral tergum without erect setae. Head, mesosoma, petiole and gaster with fine appressed pubescence which is sparse and very short on head and petiole and is sparse and extremely short on gaster.

For color see in Fig. 11 ; body orange-brown, with darker mesosoma and gaster; leg yellowish brown ( Fig. 11 ) to orange-brown, with coxae and femora paler.

Queen measurements and indices. Non-types (n=10): HW 1.87–2.17 mm, HL 2.53–2.96 mm, SL 2.49–2.76 mm, IFLW 0.42–0.57 mm, EL 0.39–0.50 mm, OL 0.12–0.18 mm, MDL 1.45–1.63 mm, WL 3.50–4.05 mm, FWL 6.46–8.33 mm, PTL 0.65–0.70 mm, PTH 1.40–1.56 mm, CI 72–76, SI 124–136, MDI 52–58, PTHI 214–229.

Queen description. In general appearance queen is similar to worker. Vertex near ocelli not swollen; ocular ridge clearly developed; distance between lateral ocelli shorter than or as long as distance between lateral and median ocelli, and as long as major axis of median ocellus; ocelli in lateral view protruded dorsad. Mesosoma with main sclerites associated with wing function ( Figs. 12 B, 12C), in dorsal view long and slender; anterodorsal slope of pronotum in lateral view gentle; anterodorsal outline of mesoscutum in lateral view relatively gentle; mesoscutum without posteromedian depression; parapsidal furrow very weak, and slightly curved; anterior third of mesopleuron with fine, oblique furrow (sometimes without any furrow); propodeum in lateral view long, with dorsum almost straight and gradually sloping posteriad. Wing venation as in Figs. 12 E and 12F. Petiolar node in lateral view, excluding apical spine with anterior and posterior faces weakly convex; apical spine short and stout, and sometimes weakly curved posteriad; subpetiolar process anteroposteriorly as long as dorsoventrally high. First gastral tergum in lateral view long, with anterior face relatively short and vertical.

Head in full-face view largely smooth and shiny, but with a striate area bordered by frontal carinae and ocular ridges; frontal lobe almost smooth and shiny; extraocular furrow faintly striate; median part of vertex along median furrow smooth and shiny or sometimes with rough texture; lateral face and venter of head smooth and shiny; median disc of clypeus smooth and shiny. Pronotum densely and weakly striate transversely (often dorsolateral part smooth and shiny); mesoscutum faintly longitudinally striate (but sometime largely smooth and shiny, and faintly striate along posterior margin of mesoscutum); mesopleuron largely smooth and shiny, with anterior third and posteriormost part faintly striate; mesoscutellum smooth and shiny; propodeum strongly and sparsely striate transversely. Petiolar node largely smooth and shiny, with its basal area faintly striate.

Pair of long erect setae present on vertex near lateral ocelli; frontal lobe with a erect seta; pronotum and 1st gastral tergum without erect setae. Head, mesosoma, and petiole with sparse subdecumbent to decumbent pubescence which is extremely short in head and gaster; mesopleuron very sparsely pubescent.

For color see in Fig. 12 ; head, mesosoma, petiole and gaster reddish brown; all coxae and femora yellowish brown; tibiae reddish brown.

Male measurements and indices. Non-types (n=10): HW 1.19–1.35 mm, HL 1.04–1.14 mm, SL 0.20–0.26 mm, EL 0.70–0.84 mm, EW 0.37–0.46 mm, OL 0.16–0.22 mm, OES 0.16–0.18 mm, WL 2.63–2.93 mm, FWL 4.52–5.58 mm, PTL 0.56–0.64 mm, PTH 0.78–0.90 mm, CI 107–120, SI 15–20, PTHI 135–152.

Male description. Size small (HL 1.04–1.14 mm, WL 2.63–2.93 mm). Major axis of median ocellus as long as minimum distance between lateral ocelli; antenna 13-merous; scape very short; 1/3 as long as 3rd antennomere; 2nd antennomere 1/2 as long as scape; 3rd to 13th antennomeres each extremely long; palp formula 6, 4; dorsal outline of clypeus in lateral view weakly convex. Mesosoma in lateral view relatively slender and long; dorsal outline of pronotum in lateral view almost straight; anterodorsal outline of mesoscutum in lateral view gently sloping; mesoscutum without median depression; parapsidal furrow very weak and almost straight; oblique mesopleural furrow relatively shallow and wide; ventrolateral part of katepisternum with very weak longitudinal furrow; propodeum in lateral view with its dorsal outline roundly convex; metapleuron separated from propodeum indistinctly by suture; wing venation similar to queen (see Figs. 12 E and 12F for queen wings). Petiolar node in lateral view tapering gently to bluntly pointed apex; its anterior slopes weakly convex, and posterior slope almost straight; subpetiolar process in lateral view anteroposteriorly shorter than dorsoventrally high, lobate and slender; petiolar sternum without posteroventral process. First gastral tergum in lateral view short; posterior spine of 8th abdominal tergum long and slender, very weakly curved (Fig. 18B); pygostyle with long setae in its apical third; disc of 9th abdominal sternum much broader than long, with posterolateral corner expanding laterad; apical lobe much longer than disc and gently tapering to almost truncate apex; telomeral apex in lateral view longer than high; distiventral apex of valviceps strongly produced; basiventral corner of valviceps distinctly produced; ventral margin of valviceps with 21−22 denticles.

Head including area between lateral ocelli entirely smooth and shiny. Pronotum in dorsal view smooth and shiny; mesoscutum smooth and shiny; scuto-scutellar suture with sparse, strong, longitudinal rugae; mesopleural anepisternum and katepisternum smooth and shiny; metapleuron smooth and shiny; propodeum in dorsal view with rough texture and shiny. Petiole smooth and shiny.

Head, mesosoma, legs, petiole and gaster with fine sparse subdecumbent to decumbent pubescence; mandible, vertex near ocelli, and gaster except 1st gastral tergum with long erect setae.

For color pattern see Fig. 13 ; males from Thailand always darker than those from the other localities.

Species recognition. The syntype workers of Odontomachus rixosus , O. rixosus conifer (ANTWEB CASENT 0907432) and O. rixosus obscurior (ANTWEB CASENT 0907431) are similar to the non-type material listed above. In the syntypes of O. rixosus and O. rixosus conifer the pronotal disc is finely striate transversely, but finely concentric in O. rixosus obscurior . Odontomachus rixosus is very similar in general appearance to O. pararixosus , but is distinguishable from the latter by the weakly notched posterior head margin (almost straight in the latter); the apical spine of the petiolar node is needle-shaped (acutely triangular in the latter); and the first gastral tergite lacks long suberect setae (present in the latter). The delimitation between O. rixosus and O. minangkabau is discussed under O. minangkabau .

Distribution. Odontomachus rixosus is distributed throughout tropical Asia: Indo-Malayan subregion (Western part of Indonesia, Malaysia, Brunei and Phillipines), India, Myanmar, Thailand, Vietnam, Cambodia and Laos.

Bionomics. Odontomachus rixosus inhabits plantations, secondary and primary forests in lowlands, and nests under leaf litter, in the soil near the base of living trees, and under rotten logs and stumps. This species has been collected nesting together with Pheidole tandjongensis (“compound colonies” GK-01-12/ GK-02-12, GK-20-12/ GK-55-12, LBT-11-12/ LBT-12-12, SAGO-06-12/ SAGO-05-12, PDG-01-12/ PDG-02-12, SU07-SKYC-204, TH03-SKY-91, TH03-SKY-152, TH91-RX-01, MP05-SKY-56, SU07-SKY-158, TH00-SKY-59, and SU07-SKY- 078) and with P. inornata Eguchi, 2001 (“compound colonies” GTH-01-12/GTH-02-12, SOO-SKY-04, TH01- SKY-07, and SB06-SKY-78). Details concerning the nature of the relationship between O. rixosus and Pheidole spp. are unknown.

DNA Barcoding. See under O. minangkabau

Figures

FIGURE 11. Odontomachus rixosus, worker (colony: PDG- 13 - 12; individual: SEMUT 141230 K): A, head in full-face view, with an arrow indicating subapical tooth of mandible; B, mesosoma in dorsal view; C mesosoma in lateral view; D petiole and gaster in lateral view.

FIGURE 12. Odontomachus rixosus, queen (colony: GTH- 01 - 12; individual: SEMUT 150102 A): A, head in full-face view; B, mesosoma in dorsal view; C, mesosoma in lateral view; D, petiole and gaster in lateral view; E, forewing; F, hindwing.

FIGURE 13. Odontomachus rixosus, male (colony: PKN- 01 - 12; individual: SEMUT 150103 A): A, head in full-face view; B, head in lateral view; C, head in dorsal view; D, mesosoma in lateral view; E, petiole in lateral view; F, mesosoma in dorsal view; G, gaster in lateral view.