Myrma

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Myrma
Polyrhachis militaris
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Formicinae
Tribe: Camponotini
Genus: Polyrhachis
Subgenus: Myrma
Billberg, 1820
Type species
Formica militaris, now Polyrhachis militaris
Diversity
184 species

Specimen labels

Synonyms

The subgenus Myrma Billberg is the most widespread of all the Polyrhachis subgenera, occurring throughout the Indo-Malayan, Oriental, Australasian and Ethiopian regions. It is also the second most speciose subgenus, comprising more than one hundred described species and subspecific forms. (Kohout 2013)

Species Groups

Currently, the Afrotropical fauna of Myrma remains divided into six species groups (alexisi, gamaii, militaris, monista, revoili and viscosa), all restricted to the region, as proposed by Bolton (1973), while the number of species-groups for the Oriental and Australasian fauna has increased to nine. Following the transfer of most of its members to the aculeata-group, the abrupta-group now comprises only a single, namebearing species, Polyrhachis abrupta from Halmahera. The parabiotica-group introduced by Kohout (2006) and the cyaniventris-group established by Sorger and Zettel (2009) each include three species, all apparently endemic to the Philippines, while the vestita-group is restricted to the Indonesian island of Sulawesi. The recently revised continua-group (Kohout 2013) comprises mostly Melanesian elements. The inermis and zopyra species-groups almost equally share the species originally included by Emery (1925) in a single zopyra-group, and both are distributed from Sri Lanka and India across Indonesia and the Philippines. Finally, the relucens-group, the largest and most widespread of the Oriental and Australasian species-groups, comprises a diverse assemblage of species that could conceivably be subdivided into several more morphologically uniform species-groups.

Afrotropical species groups

Rigato (2016) revised the Polyrachis of sub-Sahara Africa. His study retained Bolton's (1973) six species-groups for the region. There is currently a total of 61 species, all considered members of the subgenus Myrma. As for their biology "sub-Saharan Polyrhachis species have a range of nesting habits comparable to that of the whole genus: from forest species, building their nests with silk and plant debris among tree leaves, to ground inhabiting savannah ones. This life style diversity can occur in a single species-group, despite the morphological similarity of its members.

alexisi

Polyrhachis alexisi species-group

gamaii

Polyrhachis gamaii species-group

militaris

Polyrhachis militaris species-group

monista

Polyrhachis monista species-group

revoili

Polyrhachis revoili species-group

viscosa

Polyrhachis viscosa species-group

Oriental and Australasian species groups

Kohout (2008) - The continua -group is characterised by an evenly convex mesosomal outline and the presence of postocular and lateral ridges on the head. The inermis species-group was introduced by Bolton (1974). Included in the group were several species placed by Emery (1925) within the very similar zopyra-group. Both species-groups include some of the smallest members of the subgenus. The inermis -group is characterised by well developed pronotal spines, a petiole with two short lateral spines and an entire, arcuate dorsal petiolar margin, and by closely approximated frontal carinae producing an extremely narrow central area. In contrast, species included here within the zopyra-group have the pronotal spines reduced to mere teeth, a petiole armed with four, more-or-less distinct teeth and more widely separared frontal carinae and a broader central area. Twenty-seven Sulawesian species of Myrma belong within the relucens species-group, two in the inermis-group and one species each in the continua-and zopyra-groups. In addition, the island also has several endemic Myrma species that constitute a new vestita species-group characterised by a scale-like petiole that lacks spines and has a dorsal margin with only blunt teeth or a shallow median emargination. This petiolar configuration resembles that of Polyrhachis abrupta from Halmahera, but this species differs from those of the vestita-group in having strongly truncate eyes and a distinct carina running from the eyes towards the occipital corners. A petiole lacking dorsal spines is also characteristic of the inermis-group, but its constituent species differ from those of the vestita-group in having their dorsal petiolar margin smooth and entire. In addition, members of the vestita-group are some of the largest species of Myrma, while the inermis-group includes some of the smallest.

abrupta

Polyrhachis abrupta from Halmahera

aculeata

Polyrhachis aculeata species-group

Key to Polyrhachis aculeata species-group workers

continua

Polyrhachis continua species group

key to Polyrhachis continua workers

cyaniventris

Sorger and Zettel (2009, 2010); 3 species endemic to the Philippines

Polyrhachis cyaniventris species-group

Key to Polyrhachis cyaniventris species-group workers

inermis

Sri Lanka and India across Indonesia and the Philippines

Polyrhachis inermis species-group

parabiotica

Philippines

Polyrhachis parabiotic species-group

relucens

The largest and most widespread of the Oriental and Australasian species-groups, comprises a diverse assemblage of species that could conceivably be subdivided into several more morphologically uniform species-groups.

Polyrhachis relucens species-group

vestita

restricted to the Indonesian island of Sulawesi

Polyrhachis vestita species-group

zopyra

Sri Lanka and India across Indonesia and the Philippines

Polyrhachis zopyra species-group

Nomenclature

The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.

  • MYRMA [subgenus of Polyrhachis]
    • Myrma Billberg, 1820: 104. Type-species: Formica militaris, by subsequent designation of Wheeler, W.M. 1911c: 859.
    • Myrma subgenus of Polyrhachis: Forel, 1915b: 106; Forel, 1917: 251; Wheeler, W.M. 1922a: 702, 993; Emery, 1925b: 198.
    • Myrma senior synonym of Hoplomyrmus: Wheeler, W.M. 1922a: 993.
    • Myrma senior synonym of Pseudocyrtomyrma: Bolton, 1973b: 288.
    • Myrma senior synonym of Anoplomyrma: Dorow, 1995: 30.
    • [Although Myrma antedates Polyrhachis, the former has been treated as a subgenus of the latter since Forel, 1917: 251 (see Hung, 1967b: 396 for history). Dorow, Kohout & Taylor, 1997: 236 proposed the precedence of Polyrhachis over Myrma and that precedence was established by the ICZN (Opinion 1919) 1999: 92.]
  • ANOPLOMYRMA [junior synonym of Myrma]
    • Anoplomyrma Chapman, 1963: 258 [as subgenus of Polyrhachis]. Type-species: Polyrhachis (Anoplomyrma) parabiotica, by monotypy.
    • Anoplomyrma junior synonym of Myrma: Dorow, 1995: 30.
  • HOPLOMYRMUS [junior synonym of Myrma]
    • Hoplomyrmus Gerstäcker, 1859: 262. Type-species: Hoplomyrmus schistaceus, by monotypy.
    • [Hoplomyrmus also described as new by Gerstäcker, 1862: 508.]
    • Hoplomyrmus junior synonym of Polyrhachis: Roger, 1861b: 174; Roger, 1863b: 6; Mayr, 1863: 446; Dalla Torre, 1893: 257.
    • Hoplomyrmus junior synonym of Myrma: Wheeler, W.M. 1922a: 993; Emery, 1925b: 198; Bolton, 1973b: 288.
  • PSEUDOCYRTOMYRMA [junior synonym of Myrma]
    • Pseudocyrtomyrma Emery, 1921e: 18 [as subgenus of Polyrhachis]. Type-species: Polyrhachis revoili, by original designation.
    • Pseudocyrtomyrma junior synonym of Myrma: Bolton, 1973b: 288.

Description

Kohout (1989) – The subgenus Myrma Billberg can be characterised by the following combination of characters:

1. Dorsum of mesosoma convex in profile; lateral margins distinct, with margination interrupted only at the sutures.

2. Pronotum armed with a pair of relatively long, straight, more or less anteriorly-directed spines.

3. Propodeum either unarmed or with tubercles or small teeth.

4. Promesonotal suture and propodeal groove distinct.

5. Petiole scale-like, usually armed with a pair of dorsal spines or denticles, each with a laterally oriented tooth or blunt angle below its base.

6. First gastral tergite basally truncated or shallowly concave.

7. Anterior clypeal margin arcuate, often bluntly truncated medially.

8. Mandibles at their bases finely longitudinally striate.

9. Frontal carinae forming sharply raised, lamellate flanges; the area between them relatively narrow.

References