Odontomachus malignus

A coastal species with an affinity for the intertidal zone.

Identification
Sorger & Zettel (2011) - This is a unique species, morphologically defined by group characters, and ecologically defined by living in intertidal zones.

Wang et al. (2020) - Worker. With features mentioned for the Odontomachus malignus species group. Body sculpture much weaker and coloration somewhat paler than in Odontomachus litoralis. Head in full-face view with posterior margin weakly concave; median furrow deep and rather broad; head extensively and finely (often indistinctly) striate, frontal lobes and frons with stronger striae; frontal carinae short and only slightly divergent posterad. Sculpture on pronotum much weaker than in O. litoralis; separation of metapleuron from propodeum indistinct; propodeal junction not strongly angulate, showing rather round transition from dorsum to declivity, declivity laterally only weakly marginate. Petiolar node extensively smooth and shiny. Head and petiole largely dark orange-brown; mandible, antenna and gaster slightly darker brown; mesosoma disc dark reddish brown.

Male. Body relatively smaller than that of worker, body sculpture not consistently strong. Mandible falcate, apically bluntly pointed. Furrow separating metapleuron from propodeum shallow; petiolar node in anterior view with sharply or bluntly pointed apex, almost entirely smooth to superficially sculptured and shiny. Maximum diameter of lateral ocellus equal to or slightly longer than minimum distance between lateral ocellus and eye. Body almost entirely light yellowish brown with darker greyish blotches present on head and mesosomal dorsum. Basal disc of abdominal sternite IX subpentagonal with angular posterolateral corners; anterodorsal margin of valviceps weakly produced; dorsolateral carina of valviceps absent; ventral margin of valviceps undulate with ca. 33 denticles.

The workers of O. malignus from Singapore (OMSG-w) and the Philippines (OMPH-w) are similar to that of O. litoralis (OL-w), but may be distinguished from the latter by the characters listed under O. litoralis.

Distribution
Wang et al. (2020) - Distribution. Asia – Borneo (Sarawak), Indonesia (Maluku, Sulawesi (Celebes)), Philippines, Singapore; Oceania – Palau, Papua New Guinea, Solomon Islands.

Distribution based on Regional Taxon Lists
Indo-Australian Region: Borneo, Indonesia, Malaysia, New Guinea, Palau, Philippines, Singapore, Solomon Islands.

Habitat
Wang et al. (2020) - Intertidal littoral areas; workers of this species have been observed foraging in and around or emerging from exposed nest entrances in coral rubble (Brown 1976) or sheer vertical bare limestone rockfaces (Olsen 2009) along coastlines during low tides. Males were collected from mangrove forest using malaise traps, on an off-shore island in the southern part of Singapore.

Biology
Wilson (1959), Brown (1976), and Olsen (2009) describe the unusual habitat preference of O. malignus in intertidal zones. On Bantayan Island, the second author observed foraging workers in the intertidal zone of coral reef flats during low tide. On Bohol Island, one nest entrance was found in a mangrove close to the open sea. (Sorger & Zettel 2011)

Wang et al. (2020) - Odontomachus malignus, stands out for its peculiar habitat preference. This species is exclusively found in one of the harshest and most volatile places in the tropics, the intertidal littoral zone, usually on coral rubble, sometimes far from the coastline, and limestone rockfaces (Mann 1919, Wilson 1959, Brown 1976, Olsen 2009, Sorger and Zettel 2011). Little is known about the ecology and/or reproductive biology of this unusual ant, and how colonies thrive in an unstable intertidal environment subject to daily fluctuations of abiotic conditions.

The exact nesting habits of O. malignus remain largely unknown; past and present records indicative of its habitat type have been based on individual foraging workers and males caught in malaise traps. Limited anecdotal accounts and observations of O. malignus workers emerging from apparent nest entrances exposed during low tide suggest that the species possibly nests in or around coral rubble (Brown 1976), or limestone karst (Olsen 2009) next to coastlines.

Nomenclature

 * . Odontomachus malignus Smith, F. 1859a: 144 (w.) INDONESIA (Aru Is).
 * Type-material: holotype worker.
 * Type-locality: Indonesia: Aru Is, “Aru 55” (A.R. Wallace).
 * Type-depository: OXUM.
 * Status as species: Roger, 1861a: 28; Smith, F. 1863: 19; Roger, 1863b: 21; Mayr, 1863: 437; Smith, F. 1871a: 319; Emery, 1887b: 429; Emery, 1892d: 560 (in key); Dalla Torre, 1893: 51; Emery, 1911d: 113; Viehmeyer, 1914a: 112; Wheeler, W.M. 1919e: 61; Santschi, 1932b: 13; Donisthorpe, 1932c: 455; Donisthorpe, 1940c: 107; Chapman & Capco, 1951: 44; Wilson, 1959a: 495; Wilson, 1962c: 15; Brown, 1976a: 104, 159; Taylor, 1976a: 81; Bolton, 1995b: 296; Pfeiffer, et al. 2011: 56; Sorger & Zettel, 2011: 155 (redescription); Sarnat, et al. 2013: 73; Wang, W.Y. et al. 2020: 157 (redescription).
 * Senior synonym of retrolatior: Brown, 1976a: 104; Bolton, 1995b: 296; Sorger & Zettel, 2011: 156; Wang, W.Y. et al. 2020: 157.
 * Senior synonym of tuberculatus: Emery, 1887b: 429; Emery, 1892d: 560 (in key); Dalla Torre, 1893: 51; Emery, 1911d: 113; Wheeler, W.M. 1919e: 61; Wilson, 1959a: 495; Brown, 1976a: 104; Bolton, 1995b: 296; Sorger & Zettel, 2011: 156; Wang, W.Y. et al. 2020: 157.
 * Distribution: Indonesia (Aru Is, Martabello, Misool, Sulawesi), Malaysia (Sarawak), Papua New Guinea (+ New Britain), Philippines (Bantayan, Bohol, Luzon, Sulu Archipelago), Singapore, Solomon Is.
 * retrolatior. Odontomachus retrolatior Viehmeyer, 1914a: 113 (w.) NEW GUINEA (Papua New Guinea).
 * Type-material: syntype workers (number not stated, “several”).
 * Type-locality: Papua New Guinea: Monumbo.
 * Type-depository: MNHU.
 * Junior synonym of malignus: Brown, 1976a: 104; Bolton, 1995b: 297; Sorger & Zettel, 2011: 156; Wang, W.Y. et al. 2020: 157.
 * tuberculatus. Odontomachus tuberculatus Roger, 1861a: 28 (w.) (no state data).
 * Type-material: holotype worker.
 * Type-locality: unknown (“aus Asien stammt”).
 * Type-depository: MNHN or MNHU.
 * [Note: Roger says that he was sent a single worker from Paris, but does not say if he returned it.]
 * Status as species: Mayr, 1862: 711; Roger, 1863b: 22; Mayr, 1863: 437; Mayr, 1872: 149.
 * Subspecies of malignus: Mann, 1919: 305; Wheeler, W.M. 1935g: 16.
 * Junior synonym of malignus: Emery, 1887b: 429; Emery, 1892d: 560 (in key); Dalla Torre, 1893: 51; Emery, 1911d: 113; Wheeler, W.M. 1919e: 61; Wilson, 1959a: 495; Brown, 1976a: 104; Bolton, 1995b: 297; Sorger & Zettel, 2011: 156; Wang, W.Y. et al. 2020: 157.

Worker
Sorger & Zettel (2011) - Worker with smallest HW: CI 81, HL 2.25, HW 1.82, MdI 64, MdL 1.43, MsL 3.57, PnW 1.03, PtH 0.87, PtL 0.83, PtW 0.56, SI 128, SL 2.33, TL 10.00; worker with largest HW: CI 82, HL 2.82, HW 2.32, MdI 63, MdL 1.78, MsL 4.57, SI 123, SL 2.85, PnW 1.33, PtH 1.12, PtL 1.12, PtW 0.66, TL 11.13.

Structures: Mandibles long, reaching beyond midpoint of head, similar to O. infandus group. Head roughly rectangular, longer than wide, broadest at level of eyes. Conspicuous tubercles on both sides of median furrow dorso-posteriorly. Eyes located in first third of head. Dorsum of head striate, not reaching nuchal carina. Mesosoma elongate, broadest at level of pronotum. Pronotum rounded, metanotal groove in lateral view present. Very fine longitudinally oriented sculpture on pronotum; metanotum and propodeum with coarse transverse sculpture. Petiole short, truncated; short petiolar spine, anterior and posterior face flat; smooth and shiny, some fine striation may occur laterally. Gaster rounded to oval. Microsculpture on mesosoma and head finely granulate; ant appears matte.

Pilosity: Fine, loose semi-appressed white pubescence on head, mesosoma and petiole; gaster void of pubescence (some isolated hairs may occur), legs and antennae with dense white pubescence. Head with two standing setae, pronotum with some standing setae (2 - 3), setae on gaster increasing in number and length towards apex of abdomen.

Colour: Almost uniformly reddish brown, only head slightly lighter than rest.

Wang et al. (2020) - Holotype (CASENT0901334): EL 0.55; EW 0.45; HL 2.80; HW 2.30; IFLW 0.71; MDL 1.71; PTH 1.15; PTL 0.70; SL 2.86; WL 4.09; CI 82; MDI 59; PTHI 164; SI 119. Non-types (N = 6; values of PTH, PTL, SL, WL, PTHI, SI obtained from 5 out of 6 specimens – previous syntype of O. tuberculatus excluded from measurement due to extensive damage): EL 0.46–0.60; EW 0.29–0.40; HL 2.68–3.31; HW 2.15–2.73; IFLW 0.65–0.81; MDL 1.57–1.78; PTH 1.05–1.25; PTL 0.64–0.80; SL 2.80–3.08; WL 3.99–4.33; CI 80–82; MDI 54–64; PTHI 156–164; SI 127–130.

(based on holotype, Singapore and Philippine specimens). Relatively large compared to male (HL 2.70–2.80; WL 3.95–4.00). Head in full face view longer than broad, with posterior margin weakly and broadly concave; occipital carina well-developed and dark pigmented; median furrow deep and rather broad, not much darker than rest of head dorsum; bottom of furrow with weak median carina that is stronger in its anterior portion; area along each side of furrow slightly swollen; vertex posteriorly with pair of low protuberances, each located at same distance from median furrow and occipital carina; temporal prominence low; extraocular furrow shallow; ocular ridge distinctly elevated, narrow, slightly widened toward median furrow; frons somewhat distinctly differentiated from vertex especially laterally; frontal carinae very short, diverging slightly posterad, fading out into ordinary carinae on frons; distance between anterior margin of ocular ridge and anterior margin of eye subequal to major axis of eye. Mandible rather slender; masticatory mar-gin distinctly dentate with 11–12 denticles; dentition may not be equal between left and right mandibles; subapical tooth ca. 1.5–2 times as long as broad, tapering with somewhat acute apex (but not sharply pointed); apex sometimes worn and truncate. Palp formula 4, 4. Mesosoma in lateral view relatively slender compared to rest of body, constricted at mesonotum; pronotum including its anteromedian lobe (neck) rather long, in lateral view with gently sloping anterior face that is continuous to dorsal face, in dorsal view with roundly convex lateral margins; mesopleuron with carinate anteroventral ridge, which in dorsal view appears as a weak protuberance, (mesopleuron) demarcated by a distinct continuous sulcus dorsally from mesonotum and posteriorly from metapleuron (sulcus not margined with distinct carina); meta-pleuron delineated from propodeum by indistinct shallow furrow; dorsal outline of propodeum in lateral view flat to very shallowly concave; propodeal dorsum separated from declivity by weak carina with junction rounded and not strongly angulate; propodeal declivity in posterior view only weakly margined laterally. Petiolar node conical with pointed apical spine, in lateral view anterior slope almost entirely straight or weakly convex, posterior slope weakly convex and slightly steeper than anterior slope; apical spine relatively short compared to petiolar height, in frontal view gradually tapering with broad base and blunt apex, entire spine usually upright and not strongly directed posterad; subpetiolar process subtriangular with rounded apex, almost as long as high. Gastral tergite I large, in dorsal view as long as tergites II–IV combined, in lateral view with anterior slope short and vertical.

Head in full face view densely striate in most parts; frontal lobes and frons with strong striae that are longitudinal to diverging, interspaces mostly smooth and shining; anterolateral area of antennal fossa smooth and shiny; vertex with much finer striae that are often indistinct; vertex lobe, temple and lower gena with faint striation, partly micropunctate, slightly shiny; median disc of clypeus largely sculptured superficially and shiny. Dorsum and venter of mandible finely and superficially sculptured and rather shiny, lateral face smooth and shiny. Pronotum in dorsal view densely micropunctate to microreticulate with weak lustre, in lateral view irregularly striate in its anterior and posterior portions; anteromedian lobe (neck) with coarse strigae; mesonotum in dorsal view coarsely strigate with interspaces weakly microsculptured; mesopleuron densely sculptured and matte in its anterodorsal portion (upper 1/5), finely punctate but rather shiny in remaining portions, with anteriormost and posteriormost parts striate; metapleuron with sculpture similar to that of mesonotum, but with interspaces distinctly punctate. Propodeal dorsum with strigae similar to those on mesonotum; propodeal declivity with strong transverse striae that are more widely separated from each other than on propodeal dorsum. Anterior face of petiolar node mostly smooth and shiny, basally superficially sculptured with weak strigae, lateral face largely smooth and shining with median section bearing short striae, posterior face smooth and shining. Gaster mostly smooth and shining.

Head largely covered with sparse short pubescent hairs; frons posteriorly with a pair of long erect setae; mandible with scattered appressed pubescence, masticatory margin ventrally lined with multiple long yellowish setae. Dorsum of mesosoma with sparse appressed or decumbent pubescent hairs, pronotal disc with a few sparse long erect hairs. Anterior face of petiolar node with short appressed or decumbent pubescent hairs, relatively more pilose than mesosoma; posterior face of node without hairs. Entire gaster with sparse fine appressed pubescence and scattered long erect setae. Legs including coxae largely with fine but dense pubescence; ventral faces of coxae with a few sparse long erect hairs; ventral face of basal segment of protarsus with dense yellowish and stiff bristle-like hairs. Head and petiole dark orange-brown; mandible, antenna and gaster slightly darker brown, mesosoma generally darker reddish brown; legs including coxae lighter brown and more yellowish; tarsus darker brown than rest of leg.

Smith Types


Odontomachus malignus

Holotype worker in. Labelled “Aru 55,” and bearing a Donisthorpe type-label. Two other workers, similarly mounted, are in ; one is from “M” (= Mysol I.), the other is from “Mat” (= Martabello I.).

References based on Global Ant Biodiversity Informatics

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 * CSIRO Collection
 * Chapman, J. W., and Capco, S. R. 1951. Check list of the ants (Hymenoptera: Formicidae) of Asia. Monogr. Inst. Sci. Technol. Manila 1: 1-327
 * Emery C. 1887. Catalogo delle formiche esistenti nelle collezioni del Museo Civico di Genova. Parte terza. Formiche della regione Indo-Malese e dell'Australia (continuazione e fine). [concl.]. Ann. Mus. Civ. Stor. Nat. 25(5): 427-473.
 * Emery C. 1892. Voyage de M. Ch. Alluaud dans le territoire d'Assinie (Afrique occidentale) en juillet et août 1886. Formicides. Annales de la Société Entomologique de France 60: 553-574.
 * Emery C. 1911. Hymenoptera. Fam. Formicidae. Subfam. Ponerinae. Genera Insectorum 118: 1-125.
 * Emery, C. "Catalogo delle formiche esistenti nelle collezioni del Museo Civico di Genova. Parte terza. Formiche della regione Indo-Malese e dell'Australia (continuazione e fine)." Annali del Museo Civico di Storia Naturale Giacomo Doria (Genova) (2) 5, no. 25 (1887): 427-473.
 * Field Museum Collection, Chicago, Illinois (C. Moreau)
 * Janda M., G. D. Alpert, M. L. Borowiec, E. P. Economo, P. Klimes, E. Sarnat, and S. O. Shattuck. 2011. Cheklist of ants described and recorded from New Guinea and associated islands. Available on http://www.newguineants.org/. Accessed on 24th Feb. 2011.
 * Kutter H. 1933. Einige Ameisen von der Südküste von Neu-Britannien. Mitt. Schweiz. Entomol. Ges. 15: 471-474.
 * Kutter H. 1933. Einige Ameisen von der Südküste von Neu-Britannien. Mitteilungen der Schweizerischen Entomologischen Gesellschaft 15: 471-474.
 * Mann W. M. 1919. The ants of the British Solomon Islands. Bulletin of the Museum of Comparative Zoology 63:273-391.
 * Mann William. 1916. The Ants of the British Solomon Islands. Bulletin of the Museum of Comparative Zoology at Harvard College 63(7): 273-391
 * Mann, W.M. 1919. The ants of the British Solomon Islands. Bulletin of the Museum of Comparative Zoology of Harvard College 63: 273-391
 * Pfeiffer M.; Mezger, D.; Hosoishi, S.; Bakhtiar, E. Y.; Kohout, R. J. 2011. The Formicidae of Borneo (Insecta: Hymenoptera): a preliminary species list. Asian Myrmecology 4:9-58
 * Santschi F. 1932. Résultats scientifiques du voyage aux Indes orientales néerlandaises de LL. AA. RR. le Prince et la Princesse Léopold de Belgique. Hymenoptera. Formicidae. Mémoires du Musée Royal d'Histoire Naturelle de Belgique. (2)4: 11-29.
 * Smith F. 1863. Catalogue of hymenopterous insects collected by Mr. A. R. Wallace in the islands of Mysol, Ceram, Waigiou, Bouru and Timor. Journal and Proceedings of the Linnean Society of London. Zoology 7: 6-48.
 * Sorger, D.M. and H. Zettel. 2011. On the ants (Hymenoptera: Formicidae) of the Philippine Islands: V. The genus Odontomachus LATREILLE, 1804. Myrmecological News. 14:141-163.
 * Viehmeyer H. 1912. Ameisen aus Deutsch Neuguinea gesammelt von Dr. O. Schlaginhaufen. Nebst einem Verzeichnisse der papuanischen Arten. Abhandlungen und Berichte des Königlichen Zoologischen und Anthropologische-Ethnographischen Museums zu Dresden 14: 1-26.
 * Viehmeyer H. 1914. Ameisen aus Perak, Bali und Ceram (Hym.) (Freiburger Molukken-Expedition), gesammelt von E. Streesemann. Entomologische Mitteilungen. Berlin-Dahlem 3: 112-116.
 * Wheeler W. M. 1919. The ants of Borneo. Bulletin of the Museum of Comparative Zoology 63:43-147.
 * Wheeler W.M. 1935. Check list of the ants of Oceania. Occasional Papers of the Bernice Pauahi Bishop Museum 11(11):1-56.
 * Wheeler, William Morton.1935.Checklist of the Ants of Oceania.Occasional Papers 11(11): 3-56
 * Wilson E. O. 1959. Studies on the ant fauna of Melanesia V. The tribe Odontomachini. Bulletin of the Museum of Comparative Zoology 120: 483-510.
 * Wilson E.O. 1959. Adaptive shift and dispersal in a tropical ant fauna. Evolution 13(1): 122-144.
 * Wilson Edward O. 1959. Adaptive Shift and Dispersal in a Tropical Ant Fauna. Evolution 13(1): 122-144