Myrmhopla

This is currently a subgenus of Polyrhachis. Please see Polyrhachis for further information.

Species Groups
Kohout (2010) - Myrmhopla was established by Forel (1915) as a subgenus of Polyrhachis  Fr. Smith, 1857, with Formica armata (Le Guillou, 1842) as the type species. Forel did not define his new subgenus but Emery (1925) later delimited Myrmhopla  as follows (translation): “Worker. - Dorsum of thorax rounded, that is to say not marginate, except in some species (groups cryptoceroides and viehmeyeri); pronotal spines shorter than propodeal, sometimes absent; metanotal groove variable. Petiole variable amongst the groups and species; body of petiole in form of an elongate node, angled anterodorsally in profile or, to the contrary, forming a thick scale, higher than long, angular or rounded in front; generally bearing single pair of spines very variable in form, size and direction; rarely the spines are hook-like; in many species where they form a gaster embracing arc, there is between spines also a pair of teeth or small vertical spines. First gastral segment large. Female. - Very similar to the worker, with spines usually stronger and shorter.”

When Emery published his diagnosis of Myrmhopla, the subgenus already included some 140 species and subspecific forms. In an attempt to partition the high degree of diversity within such a large subgenus, he subdivided Myrmhopla into six species-groups. Dorow (1995) divided the subgenus further, recognising 16 species-groups, the six proposed by Emery and ten that he established as new. Five of these groups are relevant to the Australian fauna; the bicolor, dives , mucronata, sexspinosa and viehmeyeri-groups.

However, as mentioned by previous authors (Bolton, 1975; Dorow, 1995), the large degree of morphological diversity within Myrmhopla presents problems with maintaining the subgenus as it was originally perceived. Virtually none of the characters originally used by Emery (1925) to define Myrmhopla consistently apply to the species currently placed within the subgenus and some characters vary within a single species-group. The concept of the subgenus has widely been criticised (Hung, 1967) and the formation of numerous species-groups within Myrmhopla has only partially alleviated the problem.

Considerable morphological differences between various species-groups are evident throughout the subgenus Myrmhopla, but nowhere as markedly as in relation to the P. viehmeyeri-group. For example, a marginate mesosoma is a particularly significant character separating species of the viehmeyeri-group from the rest of Myrmhopla, except perhaps some species of the extralimital P. cryptoceroides-group (e.g. Polyrhachis cryptoceroides) (Kohout, 2006a). In some respects, viehmeyeri-group species resemble members of the subgenus Hedomyrma as they share a spinose and marginate mesosoma and a petiole featuring a more-or-less flat dorsum. However the characteristic vermiculate sculpturation, bristle-like pilosity and distinct reddish-brown colouration of species of the viehmeyeri-group clearly separate them from Hedomyrma species. The most remarkable feature of viehmeyeri-group species is their subterranean nesting habit combined with a sophisticated parasitic relationship with certain groups of ectatommine and poneroid ants (Maschwitz et al., 2003). The morphological and behavioural distinctness of the viehmeyeri-group is further supported by a preliminary molecular phylogeny of Polyrhachis (S.K.A. Robson, pers. comm.) that places the viehmeyeri -group (i.e. P. loweryi) closest to species of the subgenus Chariomyrma (Polyrhachis lata and Polyrhachis sokolova) and rather distant from representatives of other Myrmhopla species-groups. Considering these facts, I believe that the viehmeyeri-group should be removed from the subgenus Myrmhopla and a new subgenus Hirtomyrma is proposed to incorporate its constituent species.

Kohout's ideas regarding the lack of monophyly is supported by Mezger and Moreau (2015).

Regardless of the lack of clear evidence to support all of the species within these grouping, the following species groups do contain species that have been evaluated and discussed in the context of having affinities with other species and to stand apart from other groups' species. Clearly further work is needed to clarify species boundaries, species groups, and the delimitation of appropriate heirarchies and the associated nomenclature.

flavoflagellata species group
Kohout (2008) species-group worker diagnosis:

Worker. Mostly small to medium-sized ants (HL 1.15-1.85) with general characteristics of the genus. Anterior clypeal margin arcuate and entire, or medially truncate, or with a deeply emarginate median flange. Head disproportionally large compared to rest of body with eyes relatively flat, situated close to posterolateral corners. Mesosoma rather flat, laterally immarginate, humeri armed with short, triangular teeth. Propodeal spines relatively short, more-or-less horizontal, or distinctly elevated. Petiole with a pair of lateral spines that are either acute and posteriorly directed (as in e.g. P. flavoflagellata), or reduced to obtuse, laterally directed stumps (as in P. stylifera). Dorsum of petiole with a pair of short but distinct, acute intercalary spines (as in P. flavoflagellata and P. muara) or blunt tuberculae (as in P. stylifera) or smoothly rounded (as in P. storki). Head and body closely and finely punctate; gaster very finely shagreened. Hairs virtually absent from most of body, except a few, rather short, erect hairs on front of head and around gastral apex. Closely appressed, silvery or golden pubescence present in various densities over most dorsal surfaces. Mostly black, with only base of gaster and appendages sometimes light to dark reddish brown.

key to flavoflagellata species group
Key to workers of the flavoflagellata group (Kohout, 2008)

1.
Lateral petiolar spines reduced to blunt, stumplike, lateral projections (Cambodia).....stylifera Karavaiev

Lateral petiolar spines relatively long, acute, dorsoposteriorly diverging..... 2

2.
Anterior clypeal margin with deeply emarginate median flange; dorsum of petiole without intercalary teeth or spines.....storki Kohout

Anterior clypeal margin entire or simplytruncate with a shallow median emargination; dorsum of petiole with a pair of distinct intercalary spines..... 3

3.
Propodeal spines distinctly dorsoposteriorly elevated from their bases (Fig. 2); bicoloured, body black, base of gaster and appendages mostly light reddish-brown.....flavoflagellata Karavaiev

Propodeal spines more-or-less horizontal (Fig. 4); virtually unicoloured, body black, appendages black or very dark reddish-brown.....muara Kohout

sexspinosa species group
Dorow (1995):

EMERY (1925) described the workers as: "petiole long, anteriorly with an elevated angle in profile, spines inserting distally, spines relatively short and only little diverging; head long, distally narrowing; sculpture rugose; large species" (own translation). Additional data of this group are: Large slender species (TL: 8-13 mm) with an immarginate thorax. Long slender spines are present on prothorax, propodeum and petiole, only in Polyrhachis calypso the petiolar spines are curved hook-like. The head is elongately oval in frontal view. The long and spider-like legs and the antennae are round in transection, the genae are immarginate. only the neck might wear a "frill". The mat body is usually sculptured rugosely, the shiny gaster is often only finely punctate. Polyrhachis melpomene in contrast has a striate body sculpture except on the gaster. Erect hairs and appressed pubescence are usually numerous. The body colour is black, brownish or reddish.

These species arc polydomous weaver ants of the shrub and tree layer.

This group. which was established by EMERY (1925), today comprises 17 species. Polyrhachis melpomene, which was placed by EMERY (1925) into the Polyrhachis-dives-group, and Polyrhachis olybrius (=Polyrhachis olybria), which he could not associate, also belong to this species-group. BOLTON (1975) and KOHOUT (1987) (for the Philippines) revised this group.

Distribution: Australia. India. Indonesia. Malaysia, New Guinea. New Caledonia, Philippines. Solomons. Singapore. Thailand (new). This group has evolutionary centers in New Guinea and in the Philippines.

Nomenclature

 *  MYRMHOPLA [subgenus of Polyrhachis]
 * Myrmhopla Forel, 1915b: 107 [as subgenus of Polyrhachis]. Type-species: Formica armata, by original designation.
 * Myrmhopla senior synonym of Cephalomyrma, Florencea: Hung, 1967b: 402.
 * CEPHALOMYRMA [junior synonym of Myrmhopla]
 * Cephalomyrma Karavaiev, 1935a: 115 [as subgenus of Polyrhachis]. Type-species: Polyrhachis (Cephalomyrma) stylifera, by monotypy.
 * Cephalomyrma junior synonym of Myrmhopla: Hung, 1967b: 402.
 * FLORENCEA [junior synonym of Myrmhopla]
 * Florencea Donisthorpe, 1937a: 624 [as subgenus of Polyrhachis]. Type-species: Polyrhachis (Florencea) kirkae (junior synonym of Polyrhachis nigriceps), by original designation.
 * Florencea junior synonym of Myrmhopla: Hung, 1967b: 402.