Monomorium

Bolton (1987) and Hita Garcia, Wiesel and Fischer (2013) - Monomorium is a large and extremely diverse genus (~400 species) with about half of its constituent species occuring in the Afrotropical zoogeographical region. The vast majority of Monomorium species inhabit the Old World, particularly the tropics. Very few endemic species occur in North America (DuBois, 1986), and even fewer in the neotropical region where Monomorium is mostly replaced by an extensive Solenopsis fauna (Kempf, 1972). The main centres of speciation of Monomorium include Africa and Australia, with secondary centres in the Oriental region (Bingham, 1903) and Madagascar. Workers of Monomorium show a striking morphological diversity from group to group but within species-groups tend to be relatively uniform in structure. This genus contains some of the world's most widely distributed and successful tramp-species. Considering the wide distribution and species richness, it is not surprising that Monomorium are found in many terrestrial habitats and microhabitats. Astonishingly, very little is known of the natural history of most species (Ettershank, 1966). Feeding habits of most species seem to be generalistic, or more rarely granivorous. Several species are lestobiotic or parasitic and in addition, some species belong to the most successful and broadly distributed ant tramps (Ettershank, 1966; Bolton, 1987).

Identification
DuBois (1986) - Queen Antenna 12- or 11-segmented, rarely 10-segmented, with more or less distinct club of greater than 2 segments; median clypeal setae always present; clypeus usually distinctly bicarinate, carinae sharp or rounded; propodeum never with distinct teeth, rarely angulate, usually rounded; petiole distinctly pedunculate; wing venation similar to that of Salem/mix but radial cell always open; metapleural gland well developed; four Malpighian tubules with tips attached to rectum (cryptonephritic); diploid chromosome number usually 22. Worker Usually smaller than queen, remaining diagnosis same as queen, except wings lacking. Male Usually smaller than quotrn but larger than worker; Mziyrizm furrows lacking; mandible with teeth; antenna with 13 segments.

Subgenus Monomorium / Queen Antenna 12-segmented with distinct 3-segmented club (lengths of club segments increasing distally); propodeum unarmed (small bump may be present); clypeus with carinae usually extended anteriorly into teeth; masticatory border of mandible with 2-5 teeth, usually 4. Worker As in queen; promesonotal suture reduced or absent; metanotal sulcus present as pronounced constriction. Male Antennal scape cylindrical, never surpassing occiput.

Monomorium (Monomorium) minimum species group all castes: Anepisternum and katepisternum always smooth and shining; propodeum with distinct parallel longitudinal rugae on side. This species group as here understood includes only those species which are native to North and Central America. Further revisionary work within this genus may reveal this to be a paraphyletic group and may show that certain South American and Asiatic species are members of this group. However, it is a group of species (somewhat isolated geographically) well suited for revisionary study.

Regional Species List
Australian Monomorium Species

Biology
Eguchi, Bui and Yamane (2011) - Monomorium species are found in various habitats such as bare lands, grasslands, forest edges and well-developed forests. Their nests are usually found under stones and in soil. Most species forage on the ground (Eguchi & Bui 2009).

Castes
Monomorium is generally known to be polygynous, including species with winged queens, e.g., M. pharaonis (see Schmidt & al. 2011), M. subopacum; species with ergatoid queens, e.g., M. creticum (A. Buschinger, unpubl.), M. medinae (Espadaler 1982), M. hesperium (Espadaler & Agosti 1985); species with both types of queens, e.g., M. ergatogyna (Ward 2005), ''M. cf. rubriceps (Buschinger 2011), M. subapterum'' (Fersch & al. 2000). Monomorium algiricum has ergatoid queens only, and Peeters & Tinaut 2014 found both monogynous and polygynous colonies.

Nomenclature

 *  MONOMORIUM [Myrmicinae: Solenopsidini]
 * Monomorium Mayr, 1855: 452. Type-species: Monomorium minutum (junior secondary homonym in Monomorium, replaced by Monomorium monomorium), by monotypy.
 * Monomorium senior synonym of †Lampromyrmex: Wheeler, W.M. 1915h: 45; Ettershank, 1966: 82; Bolton, 1987: 287.
 * Monomorium senior synonym of Paraphacota: Santschi, 1927d: 243; Ettershank, 1966: 82; Bolton, 1987: 287.
 * Monomorium senior synonym of Epixenus: Brown & Wilson, 1957b: 244; Ettershank, 1966: 82; Bolton, 1987: 287; Tinaut & Ortiz, 1988: 167.
 * Monomorium senior synonym of Corynomyrmex, Epixenus, Epoecus, Equestrimessor, Holcomyrmex, Ireneidris, Isolcomyrmex, †Lampromyrmex (and its junior synonym Mitara), Paraphacota, Parholcomyrmex, Trichomyrmex, Wheeleria (homonym), Wheeleriella, Xenhyboma, Xeromyrmex: Ettershank, 1966: 82; Smith, D.R. 1979: 1381; Bolton, 1987: 287.
 * Monomorium senior synonym of Chelaner (and its junior synonyms Notomyrmex, Protholcomyrmex, Schizopelta): Bolton, 1987: 287.
 * Monomorium senior synonym of Antichthonidris: Heterick, 2001: 361.
 * Monomorium senior synonym of Nothidris, Phacota: Fernández, in Heterick, 2006: 79; Fernández, 2007b: 130.
 * ANTICHTHONIDRIS [junior synonym of Monomorium]
 * Antichthonidris Snelling, R.R. 1975: 5. Type-species: Monomorium denticulatum, by original designation.
 * Antichthonidris junior synonym of Monomorium: Heterick, 2001: 361.
 * CHELANER [junior synonym of Monomorium]
 * Chelaner Emery, 1914f: 410 [as subgenus of Monomorium]. Type-species: Monomorium (Chelaner) forcipatum, by subsequent designation of Emery, 1922e: 168.
 * Chelaner raised to genus: Ettershank, 1966: 93.
 * Chelaner senior synonym of Notomyrmex, Protholcomyrmex, Schizopelta: Ettershank, 1966: 93.
 * Chelaner (and its junior synonyms Notomyrmex, Protholcomyrmex, Schizopelta) junior synonym of Monomorium: Bolton, 1987: 300.
 * CORYNOMYRMEX [junior synonym of Monomorium]
 * Corynomyrmex Viehmeyer, 1916a: 133 [as subgenus of Monomorium]. Type-species: Monomorium (Corynomyrmex) hospitum, by monotypy.
 * Corynomyrmex junior synonym of Monomorium: Bolton, 1987: 287.
 * EPIXENUS [junior synonym of Monomorium]
 * Epixenus Emery, 1908f: 556. Type-species: Epixenus andrei (junior secondary homonym in Monomorium, replaced by Monomorium advena), by subsequent designation of Wheeler, W.M. 1911f: 163.
 * Epixenus junior synonym of Monomorium: Brown & Wilson, 1957b: 244; Ettershank, 1966: 82; Bolton, 1987: 292; Tinaut & Ortiz, 1988: 167.
 * EPOECUS [junior synonym of Monomorium]
 * Epoecus Emery, 1893a: cclxxvi. Type-species: Epoecus pergandei, by monotypy.
 * Epoecus junior synonym of Monomorium: Ettershank, 1966: 82; Bolton, 1987: 298.
 * ISOLCOMYRMEX [junior synonym of Monomorium]
 * Isolcomyrmex Santschi, 1917b: 296 [as subgenus of Monomorium]. Type-species: Holcomyrmex santschii (junior secondary homonym in Monomorium, replaced by Monomorium santschianum), by monotypy.
 * Isolcomyrmex junior synonym of Monomorium: Ettershank, 1966: 82; Bolton, 1987: 296.
 * †LAMPROMYRMEX [junior synonym of Monomorium]
 * †Lampromyrmex Mayr, 1868c: 93. Type-species: †Lampromyrmex gracillimus (junior secondary homonym in Monomorium, replaced by †Monomorium mayrianum), by monotypy.
 * †Lampromyrmex junior synonym of Monomorium: Wheeler, W.M. 1915h: 45.
 * †Lampromyrmex revived from synonymy as subgenus of Monomorium: Emery, 1922e: 183; Wheeler, W.M. 1922a: 676.
 * †Lampromyrmex senior synonym of Mitara: Emery, 1922e: 183; Wheeler, W.M. 1922a: 676.
 * †Lampromyrmex junior synonym of Monomorium: Ettershank, 1966: 82; Bolton, 1987: 299.
 * MITARA [junior synonym of Monomorium]
 * Mitara Emery, 1913b: 261 [as subgenus of Monomorium]. Type-species: Monomorium laeve, by original designation.
 * Mitara junior synonym of †Lampromyrmex: Emery, 1922e: 183; Wheeler, W.M. 1922a: 162, 676.
 * Mitara junior synoynm of Monomorium: Ettershank, 1966: 82; Bolton, 1987: 299.
 * NOTHIDRIS [junior synonym of Monomorium]
 * Nothidris Ettershank, 1966: 105. Type-species: Monomorium latastei, by original designation.
 * Monomorium senior synonym of Nothidris: Fernández, in Heterick, 2006: 79; Fernández, 2007b: 130.
 * NOTOMYRMEX [junior synonym of Monomorium]
 * Notomyrmex Emery, 1915i: 190 [as subgenus of Monomorium]. Type-species: Atta antarctica, by original designation.
 * Notomyrmex raised to genus: Kusnezov, 1957a: 269 (in key); Kusnezov, 1960b: 343.
 * Notomyrmex junior synonym of Chelaner: Ettershank, 1966: 93
 * Notomyrmex junior synonym of Monomorium: Bolton, 1987: 287.
 * PARAPHACOTA [junior synonym of Monomorium]
 * Paraphacota Santschi, 1919d: 90. Type-species: Paraphacota surcoufi, by monotypy.
 * [Type-species not Phacota noualhieri, unjustified subsequent designation by Santschi, 1927d: 245; this error repeated in Ettershank, 1966: 82 and Bolton, 1973a: 352.]
 * Paraphacota junior synonym of Monomorium: Santschi, 1927d: 243; Bolton, 1987: 293.
 * PHACOTA [junior synonym of Monomorium]
 * Phacota Roger, 1862b: 260. Type-species: Phacota sichelii, by monotypy.
 * Phacota junior synonym of Monomorium: Ettershank, 1966: 82.
 * Phacota revived from synonymy: Bolton, 1987: 281.
 * Monomorium senior synonym of Phacota: Fernández, in Heterick, 2006: 79; Fernández, 2007b: 130.
 * PHARAOPHANES [junior synonym of Monomorium]
 * Pharaophanes Bernard, 1967: 168, attributed to Santschi [as subgenus of Monomorium]. Type-species: Formica pharaonis, by monotypy.
 * Pharaophanes junior synonym of Monomorium: Bolton, 2003: 213.
 * [Pharaophanes Bernard, 1953b: 238, attributed to Santschi [as subgenus of Monomorium]. Unavailable name; proposed without designation of type-species. Species included by Bernard (1953b) are all referable to Monomorium: Bolton, 1987: 288; Bolton, 1995b: 42 (see also note in Baroni Urbani, 1971c: 90).]
 * PROTHOLCOMYRMEX [junior synonym of Monomorium]
 * Protholcomyrmex Wheeler, W.M. 1922a: 162 [as subgenus of Monomorium]. Type-species: Monomorium rothsteini, by original designation.
 * Protholcomyrmex junior synonym of Chelaner: Ettershank, 1966: 93.
 * Protholcomyrmex junior synonym of Monomorium: Bolton, 1987: 287, 300].
 * SCHIZOPELTA [junior synonym of Monomorium]
 * Schizopelta McAreavey, 1949: 14. Type-species: Schizopelta falcata, by original designation.
 * Schizopelta junior synonym of Chelaner: Ettershank, 1966: 93.
 * Schizopelta junior synonym of Monomorium: Bolton, 1987: 287.
 * WHEELERIELLA [junior synonym of Monomorium]
 * Wheeleriella Forel, 1907f: 145. Replacement name for Wheeleria Forel, 1905b: 171. [Junior homonym of Wheeleria Tutt, 1905: 37 (Lepidoptera).]
 * Wheeleriella junior synonym of Monomorium: Ettershank, 1966: 82; Bolton, 1987: 291.
 * XENHYBOMA [junior synonym of Monomorium]
 * Xenhyboma Santschi, 1919g: 405. Type-species: Xenhyboma mystes (junior synonym of Monomorium medinae), by monotypy.
 * Xenhyboma junior synonym of Monomorium: Espadaler, 1982: 112; Bolton, 1987: 293.
 * XEROMYRMEX [junior synonym of Monomorium]
 * Xeromyrmex Emery, 1915i: 190 [as subgenus of Monomorium]. Type-species: Formica salomonis, by original designation.
 * Xeromyrmex junior synonym of Monomorium: Ettershank, 1966: 82; Bolton, 1987: 294.

Heterick (2006) constructed the following for Malagasy Monomorium but describes what we now know to be species in the genera Monomorium, Royidris, Syllophopsis and Trichomyrmex.

Worker of Malagasy Species Minute to moderate (total length approximately 1.5–4.5 mm) monomorphic to polymorphic myrmicine ants. Palp formula 5,3, 3,3 3,2, 2,2 or 1,2. Mandible smooth or longitudinally striolate, with three to six teeth and denticles, apical tooth always much larger than the preceding tooth; basal tooth often reduced to a small or minute denticle or angle but enlarged in one species, basal tooth often separated by a diastema from remainder of the dentition in members of the Syllophopsis hildebrandti group; mandibular shape triangular, linear-triangular, or strap-like with inner and outer edges parallel or nearly so. Median clypeal seta conspicuous in most Malagasy species and positioned at or slightly above a distinct anteromedian clypeal margin except in M. hildebrandti group, where it is positioned on underside of a protruding shelf, near to the true anteromedian clypeal margin; paired setae (one often shorter than the other) straddling midpoint of anteromedian clypeal margin present in some large workers of Syllophopsis aureorugosa, Syllophopsis fisheri and Syllophopsis infusca and some queens of M. fisheri. Clypeus raised medially, usually bicarinate, though carinae may be obscure or in form of multiple weak ridges; in full-face view, the anteromedian clypeal margin often narrow and projecting, but this sector broad and abruptly declivous (i.e., when viewed in profile) in several members of M. monomorium and M. hildebrandti groups. Frontal carinae straight or diverging slightly posteriad, absent behind frontal lobes. Frontal lobes weakly sinuate or more-or-less parallel in full-face view. Antennal scrobes absent. Antennae 11- to 12-segmented; club usually with three distinct segments, sometimes four, or without a distinct club, but club never two-segmented. Eyes often reduced (sometimes to one or two ommatidia) in M. hildebrandti group, small to fairly large in other groups; in full-face view, eyes generally set at about midline of head capsule, or slightly above or below, but occasionally set well into anterior sector of head capsule; in profile, eyes usually set at about midline or behind midline of head capsule, rarely in front of midline; eye shape usually elliptical, with more pronounced curvature of the inner margin, but can be elongate or ovoid and narrowed to a point anteriad.

Mesosoma with standing setae in most groups, these setae lacking in some members of Monomorium salomonis group; standing setae short and bristle-like in members of Royidris shuckardi group. Metanotal groove most commonly deeply impressed, but weakly impressed, vestigial or absent in some taxa. Propodeal dorsum rounded onto declivitous surface, weakly or strongly angulate or armed with short denticles, spines lacking in Malagasy species; standing propodeal setae absent in some cases. Propodeal spiracle distinctly circular or nearly so, usually situated at about midlength, but placed anteriad or posteriad of midlength in some taxa, and close to propodeal dorsum in members of M. shuckardi group. Metapleural glands of moderate to small size, never hypertrophied. Propodeal lobes often small to vestigial, rarely acute-angled and prominent. Fore coxae larger than middle or hind coxae. Petiolar peduncle often with small anteroventral flange or protuberance, but this feature vestigial in many species. Petiolar spiracle well in front of node in several endemic species, slightly in front of or in anterior sector of node in remaining taxa, often rather dorsally situated. Petiolar node shape ranging from low and broadly conical or tumular to cuneate and strongly tapered, thick and asymmetrical in profile in some members of M. hildebrandti group, but never regularly cuboidal in Malagasy species; underside of node and peduncle commonly with fine, transverse rugulae in larger species of M. hildebrandti group. Anteroventral margin of postpetiolar sternites often conspicuous, this feature reduced or absent in members of Trichomyrmex destructor, Monomorium pharaonis and M. monomorium groups. Gaster dorsoventrally compressed, with blunt lateral carinae on gastral tergites. Sting not prominent in Malagasy species.

Queen of Malagasy Species Larger than conspecific worker, but not greatly so in some taxa. Palp formula, number of mandibular teeth and denticles and number of antennal segments as for conspecific worker. Ocellar triangle of three ocelli typical, but posterior ocelli may occasionally be reduced in size. Eyes large, generally elliptical, sometimes with a concavity in upper outer margin, but circular, semi-circular and ovoid eye shapes also occur.

Seen in profile, mesoscutum ranges from broadly convex to convex anteriad and flattened or even faintly sinuate posteriad. Mesoscutal pilosity always present. Pronotum, mesoscutum and mesopleuron often smooth and shining, but may be striolate or punctate to a greater or smaller degree; mesopleuron always divided by transverse furrow into upper anepisternum and lower katepisternum. Length-width ratio of mesoscutum and scutellum from near 7:3 to about 3:2. Axillae mostly well separated but may be contiguous or even reduced to a strip of thin cuticle, each individual axilla being indistinct. Metapleural sculpture most commonly in form of longitudinal striolae or striae, propodeum often unsculptured except for costulae on declivitous face, but where present frequently more marked than in conspecific worker. Dorsal propodeal face characteristically sloped, often almost vertical. Propodeal processes, where present, in form of small denticles or flanges, at most. Wing veins tubular and sclerotised in Royidris notorthotenes, Monomorium hanneli, and in M. hildebrandti group, predominantly weak and depigmented in most M. monomorium group species, though wing veins are darkly pigmented without accompanying sclerotization in some species.

Cross-vein m-cu present in all queens of M. hildebrandti group, in all M. notorthotenes queens and some M. hanneli queens, absent in other M. hanneli queens, rarely present in reproductives of M. destructor group (per Bolton 1987), and always absent in reproductives of M. monomorium and M. salomonis groups (information on the latter coming from Bolton 1987). Cross-vein cu–a always present in M. notorthotenes, M. hanneli and all members of M. hildebrandti group, always absent as a distinct vein in members of M. monomorium group (very rarely present as a vague shadow). (Alate queens seen only for M. hanneli, and M. hildebrandti, M. monomorium and M. shuckardi groups.) Petiole as for that of conspecific worker. No brachypterous queens seen among Malagasy Monomorium. Ergatoid females seen for both M. hildebrandti and M. monomorium groups.

Male of Malagasy Species I have seen males only for M. notorthotenes, M. hanneli and the M. hildebrandti and M. monomorium groups, and can associate males with just 12 of the 36 Malagasy Monomorium species identified in this work. This is too incomplete a record for a proper diagnosis to be made, but of those males seen, all, except members of the M. salomonis group, possess conspicuous, often turreted ocelli. The compound eyes are almost invariably protuberant, tending to elongate in some species. The wing of the male, on the other hand, generally has the same venation as the conspecific female, but vein cu–a is lacking in all males of M. notorthotenes and M. hanneli. The males of the endemic M. notorthotenes are very small in relation to the conspecific queen, even smaller than many workers of this species, and have a distinctly fly-like habitus. Identified males of the M. hildebrandti group are also relatively small in relation to the queen and approximately the same size or smaller than the worker. However, the size disparity between queen and male is much less among M. monomorium group reproductives, in contrast to the often minute workers, e.g. the HML of the Monomorium madecassum queen is 3.01–3.12 mm, compared with 2.80–2.84 mm for the male. (By way of contrast, the HML for the M. madecassum worker is only 1.14–1.27 mm).