Myrmhopla

Myrmhopla
	Polyrhachis abdominalis
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Hymenoptera
Family:	Formicidae
Subfamily:	Formicinae
Tribe:	Camponotini
Genus:	Polyrhachis
Subgenus:	Myrmhopla; Forel, 1915
Type species
	Formica armata, now Polyrhachis armata;
Diversity
	167 species Specimen Label

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.

Key to Australian Polyrhachis (Myrmhopla) species

arachne species group

armata species group

Polyrhachis armata species-group

bicolor species group

Polyrhachis bicolor species-group

cephalotes species group

cleophanes species group

Polyrhachis cleophanes species-group

cryptoceroides species group

Polyrhachis cryptoceroides species-group

daphne species group

dives species group

Polyrhachis dives species-group

flavoflagellata species group

nigriceps species group

ochracea species group

sexspinosa species group

Polyrhachis sexspinosa species-group

Nomenclature

The following information is derived from Barry Bolton's Online Catalogue of the Ants of the World.

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.

References

Bolton, B. 2003. Synopsis and Classification of Formicidae. Mem. Am. Entomol. Inst. 71: 370pp (page 124, Myrmhopla as subgenus of Polyrhachis)
Emery, C. 1925a [1924]. Notes critiques de myrmécologie. Ann. Soc. Entomol. Belg. 64: 177-191 (page 190, Myrmhopla as subgenus of Polyrhachis)
Forel, A. 1915b. Results of Dr. E. Mjöbergs Swedish Scientific Expeditions to Australia 1910-13. 2. Ameisen. Ark. Zool. 9(1 16: 1-119 (page 107, Myrmhopla as subgenus of Polyrhachis)
Forel, A. 1917. Cadre synoptique actuel de la faune universelle des fourmis. Bull. Soc. Vaudoise Sci. Nat. 51: 229-253 (page 251, Myrmhopla as subgenus of Polyrhachis)
Hung, A. C. F. 1967b. A revision of the ant genus Polyrhachis at the subgeneric level (Hymenoptera: Formicidae). Trans. Am. Entomol. Soc. 93: 395-422 (page 402, Myrmhopla senior synonym of Cephalomyrma, Florencea)
Klimeš, P., Drescher, J., Buchori, D., Hidayat, P., Nazarreta, R., Potocký, P., Rimandai, M., Scheu, S., Matos-Maraví, P. 2022. Uncovering cryptic diversity in the enigmatic ant genus Overbeckia and insights into the phylogeny of Camponotini (Hymenoptera:Formicidae:Formicinae). Invertebrate Systematics, 36(6), 557-579 (doi:10.1071/is21067).
Kohout, R.J. 2009a. A new species of the Polyrhachis (Myrmhopla) flavoflagellata-group from Borneo. Asian Myrmecology 2 (2008): 11-16.
Kohout, R.J. 2010. A review of the Australian Polyrhachis ants of the subgenera Myrmhopla Forel and Hirtomyrma subgen. nov. Memoirs of the Queensland Museum – Nature 55: 167-204.
Mezger, D. and Moreau, C. S. 2015. Out of South-East Asia: phylogeny and biogeography of the spiny ant genus Polyrhachis Smith (Hymenoptera: Formicidae). Systematic Entomology. 41:369–378. doi:10.1111/syen.12163
Robson, S. 2020. Spiny Ants (Polyrhachis). Encyclopedia of Social Insects, pp. 1–6. (doi:10.1007@978-3-319-90306-4_115-1).
Wheeler, W. M. 1922i. Ants of the American Museum Congo expedition. A contribution to the myrmecology of Africa. VII. Keys to the genera and subgenera of ants. Bull. Am. Mus. Nat. Hist. 45: 631-710 (page 701, Myrmhopla as subgenus of Polyrhachis)