Myrmosaga

Myrmosaga
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Hymenoptera
Family:	Formicidae
Subfamily:	Formicinae
Tribe:	Camponotini
Genus:	Camponotus
Subgenus:	Myrmosaga; Forel, 1912
Type species
	Camponotus kelleri Specimen labels;
Synonyms
	Myrmopytia Emery, 1920;

Overview of Genus Rakotonirina and Fisher (2022) - Members of Myrmosaga are found only in Madagascar and surrounding islands of the southwest Indian Ocean region. They occupy all the terrestrial ecoregions encountered in this region. Morphologically, the worker castes of the subgenus present a wide range of features that are the result of its substantial adaptive radiation across these islands, but particularly in Madagascar. Several species within the subgenus show development of a few or many characters similar to fauna from the Afrotropical region.

This proposed Myrmosaga classification is based on the use of additional morphological features thought to be relevant in defining the subgenus more precisely. Minor workers of Myrmosaga are generally characterized by the combination of the following morphological characters: clypeus medially carinate, mandible armed with six teeth, laterodorsal angle of mesosoma never marginate, petiolar node never conical.

Diagnosis The following is based on Rakotonirina and Fisher, 2022.

As for most Camponotus species, minor and major worker castes exist within a colony of the subgenus Myrmosaga. In addition, various worker forms showing continuous morphological variation between these two castes are observed. The following combination of characters can be used to reliably distinguish the two extreme worker castes in the subgenus Myrmosaga from other Malagasy subgenera and species groups of Camponotus.

Minor worker

Head elongate in full-face view, sides either converging or diverging posteriorly towards eye level to approximately parallel to each other and start rounding to posterior margin at ca. posterior 1/3 to posterior 1/5; posterior margin sometimes indistinct from lateral margins.

Mandible triangular, apical margin armed with six teeth. In some species, two apical teeth closer to each other than the other teeth.

Palp formula: 6,4.

Clypeus with median carina, its anteromedian margin mostly broadly convex, sometimes straight (C. dufouri, C. lubbocki, C. gibber, C. rotrae, C. immaculatus, etc.), projecting into triangular lobe (C. sambiranoensis, C. liandia); anterior margin rarely excised medially (C. lokobe).

Antenna with 12 antennomeres, elongate flagellomeres; antennal scape long, generally its distal 1/2 surpassing posterior cephalic margin, either covered or without erect hairs; apical antennomere slightly longer than other flagellomeres;

Frontal lobe narrow and partially covering the antennal insertion; frontal carina S-shaped, strongly divergent posteriorly.

Compound eye large, most often protruding, its posterior margin usually located at ca. posterior 1/3 to posterior 1/4 of the head.

Mesosoma in lateral view, ranging from long and low (C. dufouri, C. lokobe, C. atimo, C. vano, etc.) to short and high (C. cemeryi); or with pronotum and mesonotum weakly convex, mesonotum and propodeum almost straight (C. hovahovoides).

Promesonotal suture visible.

Pronotum with rounded junction between its dorsum and lateral face; humeral angle rounded.

Mesopleuron and propodeal surface together clearly longer than lateral portion of pronotum in lateral view.

Metapleural gland absent.

Metanotal groove inconspicuous to clearly visible.

Procoxa of normal size, maximum width as large as, or smaller than, width of mesopleuron.

Middle and hind tibiae with single pectinate spur.

Tibia of hind leg either axially rounded or rarely twisted basally.

Petiolar node laterally narrow and low.

Gaster generally elongate and narrow, anteriorly low and short.

Sculpture varying from smooth and shiny through finely and densely imbricate to generally matte.

Major worker

Major worker similar to minor worker, but characterized by the following distinctive traits: larger, heart-shaped head; less protruding eye not breaking lateral cephalic margin; more robust mesosoma; stronger mandibles (armed with at least seven teeth and denticles); clypeus with anterolateral angle and straight anterior margin; antennal scape shorter, at most apical 1/3 extending beyond posterior margin of head; metanotum distinctly visible; petiolar node much higher than long (more flattened anteroposteriorly); more erect hairs on promesonotum and the junction of propodeal dorsum and declivity.

Myrmosaga Species

Key to Myrmosaga minor workers

Rakotonirina and Fisher (2022)

Geographical Distribution of Species Madagascar and surrounding islands of the southwest Indian Ocean region

Notes Rakotonirina and Fisher (2022) - Originally Forel (1912) created Myrmosaga as a separate subgenus of Camponotus. Its synonymy under Mayria by Emery (1925) was based on similarity in the form of the clypeus, number of mandibular teeth, and shape of the mesosoma, and the petiole. It also was based on insufficient samples and comparative studies of different species belonging to these two subgenera. In the present study, we revealed many characters (see the Morphological diagnosis above) to distinguish Myrmosaga from Mayria. Members of Mayria are differentiated by the combination of the following characters: the clypeus lacks median carina, its anterolateral corner is rounded; the anterior margin of the pronotum is strongly convex in lateral view, forming a rounded flange and extended laterally to form an obtuse humeral angle; in dorsal view, the pronotal disc is rectangular with distinct lateral margins; the propodeum dorsum is never concave. Thus, Myrmosaga is revived from this synonymy here.

Nomenclature

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

MYRMOSAGA [subgenus of Camponotus]
- Myrmosaga Forel, 1912i: 92 [as subgenus of Camponotus]. Type-species: Camponotus kelleri, by subsequent designation of Wheeler, W.M. 1913a: 81.
- [Type-species not Camponotus quadrimaculatus, unjustified subsequent designation by Forel, 1914a: 260.]
- Myrmosaga junior synonym of Mayria: Emery, 1925b: 121.
- Myrmosaga as subgenus of Camponotus: Rakotonirina & Fisher, 2022.
MYRMOPYTIA [junior synonym of Myrmosaga]
- Myrmopytia Emery, 1920b: 243 [as subgenus of Camponotus]. Type-species: Camponotus imitator Forel, 1891b: 209, by original designation.
- Myrmopytia as subgenus of Camponotus: Emery, 1920b: 243; Wheeler, W.M. 1922a: 707; Emery, 1925b: 114; subsequent authors; Bolton, 1995b: 38; Bolton, 2003: 117.
- Myrmopytia as junior synonym of Myrmosaga: Rakotonirina & Fisher, 2022: 14.

References

Arnold, G. 1922. A monograph of the Formicidae of South Africa. Part V. Myrmicinae. Ann. S. Afr. Mus. 14: 579-674 (page 613, Myrmosaga as subgenus of Camponotus)
Bolton, B. 2003. Synopsis and Classification of Formicidae. Mem. Am. Entomol. Inst. 71: 370pp (page 113, Myrmosaga as junior synonym of Mayria)
Emery, C. 1920b. Le genre Camponotus Mayr. Nouvel essai de la subdivision en sous-genres. Rev. Zool. Afr. (Bruss.) 8: 229-260 (page 241, Myrmosaga as subgenus of Camponotus)
Emery, C. 1925d. Hymenoptera. Fam. Formicidae. Subfam. Formicinae. Genera Insectorum 183: 1-302 (page 121, Myrmosaga as junior synonym of Mayria)
Forel, A. 1912j. Formicides néotropiques. Part VI. 5me sous-famille Camponotinae Forel. Mém. Soc. Entomol. Belg. 20: 59-92 (page 92, Myrmosaga as subgenus of Camponotus [Type-species not Camponotus quadrimaculatus, unjustified subsequent designation by Forel, 1914a: 260.] )
Forel, A. 1914a. Le genre Camponotus Mayr et les genres voisins. Rev. Suisse Zool. 22: 257-276 (page 260, Myrmosaga as subgenus of Camponotus)
Forel, A. 1917. Cadre synoptique actuel de la faune universelle des fourmis. Bull. Soc. Vaudoise Sci. Nat. 51: 229-253 (page 250, Myrmosaga as subgenus of Camponotus)
Rakotonirina, J.C., Fisher, B.L. 2022. Revision of the Malagasy Camponotus subgenus Myrmosaga (Hymenoptera, Formicidae) using qualitative and quantitative morphology. ZooKeys 1098: 1–180 (doi:10.3897/zookeys.1098.73223).
Wheeler, W. M. 1913a. Corrections and additions to "List of type species of the genera and subgenera of Formicidae". Ann. N. Y. Acad. Sci. 23: 77-83 (page 81, Type-species: Camponotus kelleri, by subsequent designation)
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 706, Myrmosaga as subgenus of Camponotus)