Odontomachus simillimus

Found in clearings and secondary growth throughout the Indo-Pacific.

Identification
Sorger & Zettel (2011) - Odontomachus simillimus can be easily recognised even in the field by small size, dark colour, proportionally large head and short scape. In the Philippines, there is no other species with a short, truncate subapical tooth of the mandible, and none with fine reticulation on visible part of gaster tergite 2 (but note that the anterior part of tergite 2 which is usually covered by tergite 1 is also reticulate in other species).

Odontomachus simillimus is surprisingly uniform over its large distribution area. It is distinguished from the second Old World species, Odontomachus troglodytes from Africa, Madagascar, and the Seychelles, by its smooth gaster tergite 1.

Satria et al. (2015) - Odontomachus simillimus is easily separated from the other Sumatran species of the genus by the following characteristics of the worker: subapical teeth blunt and short; palp formula 4, 3; pronotal disc and first gastral tergum with several long erect setae. This species is also distinguishable from the other Sumatran species by the following characters of the male: palp formula 6, 3; dorsal outline of clypeus in lateral view much convex; propodeum in lateral view with its dorsal outline angulate; disc of 9th abdominal sternites broader than long, almost as long as apical lobe, with straight basal margin; apical lobe slightly narrower in basal half, with apical margin weakly convex; telomeral apex in lateral view as long as high; vental margin of valviceps with 34–36 denticles; body largely blackish brown, with mandible and small area of clypeus and anterior of head yellowish, and antenna yellowish brown.

Fisher and Smith (2008) - Workers and males are very similar in morphology and size to Odontomachus troglodytes. Bivariate plots of metric measurements did not distinguish the two species. Workers and queen have fine, glossy dorsal striation on head and mesosoma. Metasternal process low and rounded. Metasternal process can be viewed in mounted specimens by removing a hind leg and coxa. Brown (1976) provides a description and references.

Distribution
Sorger & Zettel (2011) - Widely distributed from India to Polynesia (Wilson 1959, Brown, 1976), “undoubtedly many of the island records represent accidental introductions by man” (Brown 1976: 87). No distribution limit in the Philippines; records from 21 islands (19 in this study).

Distribution based on Regional Taxon Lists
Afrotropical Region: Mozambique. Australasian Region: Australia, New Caledonia. Indo-Australian Region: Borneo, Fiji, Guam, Indonesia , Kiribati, Krakatau Islands, Malaysia, Marshall Islands, Micronesia (Federated States of), New Guinea, Niue, Northern Mariana Islands, Palau, Philippines, Samoa, Solomon Islands, Tonga, Wallis and Futuna Islands. Oriental Region: Bangladesh, Cambodia, India, Laos, Nicobar Island, Sri Lanka, Thailand, Vietnam.

Habitat
Sorger & Zettel (2011) - Odontomachus simillimus is a common species which also can be found in open or moderately to strongly disturbed habitats, like coastal areas, coconut groves, villages, and even lawns on university campuses. It usually does not enter dense forests, but can be occasionally found on banks of stream running through forests. According to collections by Chapman in eastern Negros, the species can be found from sea level up to an elevation of 900 m (Wheeler and Chapman 1925).

Biology
Satria et al. (2015) - Odontomachus simillimus is a common species in gardens and green patches in residential zones, plantations, and secondary forests. Nests are usually found in the soil near the base of living trees, and under shelters (such as stumps, rotten logs and rocks), but sometimes under paved floors around houses.

In Bali, we found two colonies of O. simillimus near the base of living trees in a cacao plantation which coexisted with colonies of the myrmicine Pheidole ghigii. However, the coexistence between the two species seems to be occasional because we have not yet found such cases in Krakatau and Sumatra. Any other ant partner of O. simillimus has not yet been found.

Nomenclature

 *  simillimus. Odontomachus simillimus Smith, F. 1858b: 80, pl. 5, figs. 8, 9 (q.) FIJI IS. Mayr, 1867a: 79 (w.); Karavaiev, 1925c: 294 (m.); Wheeler, G.C. & Wheeler, J. 1980: 530 (l.); Imai, Brown, et al. 1984: 67 (k.); Tjan, Imai, et al. 1986: 57 (k.). Junior synonym of haematodus: Roger, 1861a: 24; Mayr, 1865: 64; Emery, 1911d: 114. Revived from synonymy: Wilson, 1959a: 499; Brown, 1976a: 106. Senior synonym of fuscipennis: Wilson, 1959a: 499; of breviceps, pallidicornis: Brown, 1976a: 106. See also: Brown, 1976a: 165; Fisher & Smith, 2008: 15; Sorger & Zettel, 2011: 158.
 * pallidicornis. Ponera pallidicornis Smith, F. 1860a: 73 (m.) INDONESIA (Sulawesi). Combination in Euponera (Brachyponera): Donisthorpe, 1932c: 458; in Odontomachus: Brown, 1976a: 106. Junior synonym of simillimus: Brown, 1976a: 106.
 * fuscipennis. Odontomachus haematodes var. fuscipennis Forel, 1913k: 19 (w.q.m.) SRI LANKA. Junior synonym of simillimus: Wilson, 1959a: 499.
 * breviceps. Odontomachus haematoda var. breviceps Crawley, 1915b: 239 (w.) CHRISTMAS I. Junior synonym of simillimus: Brown, 1976a: 106.

Type Material


Ponera pallidicornis

Holotype male in. Labelled “Mak” (= Makassar, Sulawesi) and with a Donisthorpe type-label.

Odontomachus simillimus

Type-localities are give as Fiji, and secondarily Ceylon (= Sri Lanka). As far as can be ascertained, all the types were queens. I can find no trace of any Smith material from these localities at, where the only specimen present in Smith’s collection is a dealate queen from Waigeo I., New Guinea.

In there is a single, damaged queen from Ceylon which may be one of the original type-series, labelled “Ceylon. 50/56,” and also with a “Farren White” label. Acc. Reg.: “1850 no. 56 (June 17) Ceylon. Presented by Dr Joseph Hooker FRS.” In addition, has a single, headless, alate queen from Fiji, without further data, that may be one of the original specimens.

Determination Clarifications
Known though most of the literature as O. haematode (Linnaeus) 1758, which is a different species (Fisher and Smith 2008).

Worker
Sorger & Zettel (2011) - Worker with smallest HW: CI 83, HL 1.97, HW 1.63, MdI 53, MdL 1.05, MsL 2.43, SI 108, SL 1.77, PnW 0.87, PtH 0.75, PtL 0.64, PtW 0.38, TL 7.63; worker with largest HW: CI 82, HL 2.52, HW 2.07, MdI 53, MdL 1.33, MsL 2.93, PnW 1.13, PtH 0.89, PtL 0.99, PtW 0.52, SI 106, SL 2.20, TL 11.06.

Structures: Mandibles short and stout, with very fine denticles, sometimes completely edentate but always with three apical teeth (intercalary tooth slightly shorter than apical and subapical teeth). Apex of mandibles with some setae. Mandibles mostly smooth, some fine ridges / striae may occur, with fine white pubescence, hair pits distinct. Head in dorsal view rectangular, longer than wide, broadest at level of eyes which do not surpass outline of head. Dorsum of head striate, striation almost reaching nuchal carina (at dorsal margin, area of about the width of the scape, smooth). Eyes located dorsolaterally in first third of head. Mesosoma elongate in dorsal view, broadest at level of pronotum. Pronotum with round striation, often slightly oval or longitudinal in centre, but some entire circles always visible in dorsal view. Mesonotum and propodeum with transverse striation (slightly coarser on propodeum). Mesopleuron smooth in centre, some striation at margins. Metanotal spiracle inconspicuous, situated dorsolaterally. Petiole short and straight, conspicuously “tear-shaped” in frontal view, broad with short petiolar spine, posteriorly flat with transverse striation. Gaster rounded to oval; anterior part of first tergite evenly convex in lateral aspect, without impression; first tergite smooth, second with some reticulation, at least anteriorly.

Pilosity: Fine white semi-appressed pubescence on entire body, very dense on appendages including petiole, on mesosoma, head and gaster distance between hairs approximately their length. Few standing setae on pronotum, several standing hairs on gaster increasing in length towards apex of abdomen. Some isolated hairs on head venter and one pair of standing setae on head dorsum.

Colour: Body, including all appendages, dark brown (almost black in some specimens).

Satria et al. (2015) - (n=10): HW 1.72–2.26 mm, HL 2.12–2.73 mm, SL 1.97–2.43 mm, IFLW 0.50–0.65 mm, EL 0.34–0.42 mm, MDL 1.15–1.50 mm, WL 2.66–3.29 mm, PTL 0.46–0.57 mm, PTH 1.02–1.28 mm, CI 76–83, SI 106–116, MDI 52–56, PTHI 212–236.

Relatively small (HL 2.12–2.73 mm; WL 2.66–3.29 mm). Head in full-face view slightly longer than broad, with posterior margin strongly concave; median furrow on vertex present as dark line; each side of line weakly humped; frontal lobes followed by weak frontal carinae which are divergent posteriad; minimum distance between margin of ocular ridge and margin of compound eye less than half of major axis of compound eye; mandible relatively stout; masticatory margin with small denticles or edentate; subapical tooth shorter than broad, blunt at apex; palp formula 4, 3. Mesosoma in lateral view stout; pronotum including its anteromedian lobe short, in lateral view with anterodorsal slope steep; mesopleuron with conspicuous anteroventral ridge, with anterodorsal margin distinctly carinate, clearly separated by distinct dorsal carina from mesonotum and metapleuron; propodeum in lateral view with dorsum slightly convex and gradually sloping posteriad, 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 almost straight anteriorly and very weakly convex posteriorly; apical spine short and slender, 1/4 as long as petiolar height, sometimes weakly curved posteriad; subpetiolar process anteroposteriorly longer than dorsoventrally high, triangular, directed posteriorly. First gastral tergum in lateral view short, with anterior face long and vertical.

Head in full-face view extensively striate, with area between eye and frontal lobe and area around eye smooth and shiny; frontal lobe finely and faintly striate; extraocular furrow striate; median part of vertex along median furrow striate; lateral face weakly striate; venter of head completely or largely smooth and shiny; median disc of clypeus with rough texture. Pronotal disc in dorsal view densely with concentric striation; mesonotum densely striate transversely; mesopleuron largely smooth and shiny, but with anterior third finely striate; metapleuron moderately striate; lateral face of propodeum with transverse striation which is a little sparser and stronger than mesonotum; dorsum and posterior face of propodeum coarsely and transversely striate. Petiolar node weakly striate anteriorly and laterally; posterior face of node weakly striate or sometimes smooth and shiny.

Vertex with a pair of long erect setae; frontal lobe without seta; pronotal disc and first gastral tergum with long erect setae, as long as setae on vertex. Head (except its venter), mesosoma, petiole and gaster with dense subdecumbent to decumbent pubescence; venter of head with sparse appressed pubescence.

Body reddish brown to dark brown (nearly black).

Fisher and Smith (2008) - Measurements: maximum and minimum based on n = 10 from Madagascar: HL 2.33–2.63, HW (across vertex) 1.64–2.03, HW (across upper eye margin) 1.77–2.06, CI 75–81, EL 0.20–0.23, ML 1.14–1.28, MI 48–51, SL 2.16–2.43, SI 109–123, WL 2.62–3.06. FL 2.29–2.56, PW 1.02–1.24.

Queen
Satria et al. (2015) - (n=10): HW 2.07–2.17 mm, HL 2.49–2.69 mm, SL 2.22–2.39 mm, IFLW 0.60–0.68 mm, EL 0.45–0.52 mm, OL 0.08–0.11 mm, MDL 1.31–1.45 mm, WL 3.19–3.29 mm, FWL 6.56–6.86 mm, PTL 0.56–0.60 mm, PTH 1.40–1.48 mm, CI 80–85, SI 102–114, MDI 50–55, PTHI 232–256.

In general appearance queen is similar to worker. Vertex near ocelli swollen; ocular ridge faintly developed; distance between lateral ocelli as long as distance between lateral and median ocelli, and 3.5 times as long as major axis of median ocellus; ocelli in lateral view with not protruded dorsad. Mesosoma with main sclerites associated with wing function, in dorsal view short and stout; anterodorsal slope of pronotum in lateral view relatively steep; anterodorsal outline of mesoscutum in lateral view relatively gentle; mesoscutum without posteromedian depression; parapsidal furrow very weak and slightly curved; mesopleuron without oblique furrow; propodeum relatively long, in lateral view with dorsum almost straight and sloping gradually posteriad. Wing venation as in Figs. 3E and 3F. Petiolar node in lateral view, excluding apical spine with anterior face faintly to weakly concave and posterior face faintly convex; apical spine very short and slender, and curved posteriad; subpetiolar process anteroposteriorly longer than dorsoventrally high. First gastral tergum in lateral view relatively short, with anterior face long and vertical.

Head in full-face view extensively striate, with area between eye and frontal lobe, and area around eye smooth and shiny; frontal lobe finely and faintly striate; extraocular furrow striate; median part of vertex along median furrow striate; lateral face weakly striate; venter of head completely or largely smooth and shiny; median disc of clypeus with rough texture. Pronotum weakly striate transversely; mesoscutum with dense longitudinal striation; striation finer on mesoscutum than on pronotum and propodeum; mesopleuron largely smooth and shiny, but with posteriormost part faintly striate; mesoscutellum smooth and shiny; propodeum strongly striate transversely. Petiolar node excluding apical spine entirely striate, but striation on anterior and posterior faces weaker than that on lateral face.

Pair of long erect setae present on vertex near lateral ocelli; frontal lobe without erect seta; pronotal disc and first gastral tergum with long erect setae, as long as setae on vertex near lateral ocelli. Head, mesosoma, petiole and gaster with dense subdecumbent to decumbent pubescence, except mesopleuron very sparsely pubescent.

Body reddish brown to dark brown (nearly black).

Sorger & Zettel (2011) - Gyne with smallest HW: CI 87, HL 2.27, HW 1.97, MdI 57, MdL 1.30, MsL 2.93, PnW 1.60, PtH 1.00, PtL 0.78, PtW 0.49, SI 107, SL 2.10, TL 9.88; gyne with largest HW: CI 85, HL 2.47, HW 2.10, MdI 54, MdL 1.33, MsL 3.13, PnW 1.65, PtH 1.02, PtL 0.88, PtW 0.61, SI 104, SL 2.18, TL 10.31.

Structures: Differs only in the following characters: pronotum with transverse striation, mesonotum with longitudinal striation, scutellum shiny, sexual female morph-specific characters (wing insertions, mesosoma and gaster bigger).

Fisher and Smith (2008) - Measurements: maximum and minimum based on n = 5 from Madagascar: HL 2.37–2.55, HW (across vertex) 1.79–2.03, HW (across upper eye margin) 1.87–2.13, CI 79–84, EL 0.49–0.53, ML 1.17–1.30, MI 49–52, SL 2.15–2.38, SI 111–118, WL 3.13–3.19. FL 2.36–2.58.

Male
Satria et al. (2015) - (n=10): HW 1.16–1.28 mm, HL 0.95–1.14 mm, SL 0.17–0.21 mm, EL 0.59–0.68 mm, EW 0.34–0.40 mm, OL 0.15–0.18 mm, OES 0.21–0.26 mm, WL 2.66–2.99 mm, FWL 4.60–5.48 mm, PTL 0.46–0.64 mm, PTH 0.81–0.95 mm, CI 104–129, SI 14–17, PTHI 147–176.

Size small (HL 0.95–1.14 mm; WL 2.66–2.99 mm). Major axis of median ocellus smaller than 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, 3; dorsal outline of clypeus in lateral view strongly convex. Mesosoma in lateral view relatively stout and short; dorsal outline of pronotum in lateral view strongly convex; anterodorsal outline of mesoscutum in lateral view steeply slooping; mesoscutum without median depression; parapsidal furrow weak and almost straight; oblique mesopleural furrow relatively deep and wide; ventrolateral part of katepisternum with weak longitudinal furrow; propodeum in lateral view with its dorsal outline angulate; metapleuron distinctly separated from propodeum by a suture; wing venation similar to queen. Petiolar node in lateral view tapering to blunt apex; its anterior slope in lateral view very weakly sinuate, and its posterior slope straight and steeper; subpetiolar process in lateral view anteroposteriorly as long as dorsoventrally high, triangular and thick; petiolar sternum with conspicuously angulate process posteroventraly. First gastral tergum in lateral view short; posterior spine of 8th abdominal tergum long and slender, very weakly curved (but variable in shape within species); pygostyle digitiform, with long setae in apical half; disc of 9th abdominal sternites broader than long, almost as long as apical lobe, with straight basal margin; apical lobe slightly narrower in basal half, with apical margin weakly convex; telomeral apex in lateral view as long as high; distiventral apex of valviceps strongly produced; basiventral corner of valviceps distinctly produced; ventral margin of valviceps with 34–36 denticles.

Head including area between lateral ocelli largely smooth and shiny, with clypeus faintly striate; venter of head faintly striate and shiny. Pronotum largely smooth and shiny, with lateral part faintly striate; mesoscutum faintly rugoso-reticulate and opaque; scuto-scutellar suture with very sparse, weak, longitudinal rugae; mesopleuron with anepisternum smooth and shiny, and katepisternum largely smooth and shiny, but with faint and rough texture in posteriormost part; propodeum including its posterior slope with rough texture. Petiole faintly striate to rugose.

Head, mesosoma, legs, petiole, and gaster with fine dense subdecumbent to decumbent pubescence; apex of mandible, vertex near ocelli, pronotum and gaster with several long erect setae.

Head, mesosoma, legs, petiole, gaster blackish brown; antenna yellowish brown; frons and clypeus largely yellowish brown, with lateral part of clypeus and the areas in front of antennal insertions rather yellow; mandible yellow.

Fisher and Smith (2008) - Measurements: maximum and minimum based on n = 1 from Madagascar: HL 0.89, HW 1.19, CI 133, EL 0.59, SL 0.19, SI 16, WL 2.44. FL 1.73.