Megaponera

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Megaponera
Megaponera analis
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Ponerinae
Tribe: Ponerini
Alliance: Odontomachus genus group
Genus: Megaponera
Mayr, 1862
Type species
Formica foetens, now Megaponera analis
Diversity
6 species
(Species Checklist)

Pachycondyla analis sam-hym-c008323b profile 1.jpg

Pachycondyla analis sam-hym-c008323b dorsal 1.jpg

Specimen Label

At a Glance • Ergatoid queen  

 

Megaponera is a monotypic genus, with an additional five subspecies, widespread in Sub-Saharan Africa. It is notable for its ergatoid queens, polymorphic workers, obligate group foraging, and specialized termite predation.

Identification

Schmidt and Shattuck (2014) - Diagnostic morphological apomorphies of Megaponera workers include the presence of preocular carinae and size polymorphism, which do not occur in combination in any other ponerine. Preocular carinae occur in Odontoponera and many Neoponera species, but Megaponera lacks Odontoponera’s striate sculpturing and denticulate clypeus, and Neoponera’s prominent white projecting arolia, simple tarsal claws and U-shaped cuticular lip posterior to the metapleural gland orifice.

Keys including this Genus

 

Distribution

Megaponera is widespread in tropical Sub-Saharan Africa. Wheeler (1922b) shows the range as encompassing the African continent from roughly 10° N latitude to 30° S latitude.

Distribution and Richness based on AntMaps

Biology

Megaponera analis has an unusual suite of ecological, behavioral, and social adaptations relative to most ponerines. The typical ponerine species has small colonies (usually fewer than 100 individuals), alate queens, and monomorphic workers which forage singly. Megaponera has diverged significantly from this basic pattern, having relatively large colonies, flightless queens, and polymorphic workers which are specialized mass raiders of termites.

Megaponera nests in the ground, in deserted termite mounds, or even partially in rotting logs (Lèvieux, 1976B; Longhurst & Howse, 1979a), and has relatively large colonies by ponerine standards, with from 500 to 2,000 workers (Peeters, 1991b; Hölldobler et al., 1994). The nests are host to a diverse assemblage of myrmecophiles (Arnold, reprinted in Wheeler, 1922b). Colonies have a single highly fecund ergatoid queen, which in most respects resembles a large major worker but is endowed with a rich array of glands for chemical communication with the workers (Peeters, 1991b; Hölldobler et al., 1994). Males locate virgin queens by following the recruitment trails of workers back to their nests (Longhurst & Howse, 1979b). Workers retain spermathecae and ovarioles, but do not appear to mate and do not produce viable haploid eggs (Villet, 1990a; Villet & Duncan, 1992). Workers are continuously polymorphic for size (Longhurst & Howse, 1979a; Crewe et al., 1984), though they are often referred to as “majors”, “medias” and “minors”. They are known to emit a strong odor, to stridulate loudly when disturbed, and to have a very painful sting (Arnold, 1915).

Megaponera are specialized mass raiders of termites (Wheeler, 1922b, 1936; Weber, 1964; Lévieux, 1966). Longhurst & Howse (1979a) studied their foraging behavior in detail and described the sequence of events in a typical raid (see also the account by Weber, 1964). Raids begin when a solitary major worker locates foraging termites. This scout returns directly to its nest, laying a trail of poison gland-derived pheromones exuded through its sting (Longhurst et al., 1979A), and recruits up to several hundred of its nestmates (Corbara & Déjean, 2000). They proceed as a column to the termites’ protected foraging tunnels, which the major workers tear open. Minor workers then haul out termites. When this process is complete, the major workers stack the termites in their mandibles and the ants return as a column to their nest. Corbara & Déjean (2000) compared the behavior of minor and major workers during prey capture and found that though they are generally similar, major workers are more likely to attack termite soldiers than are minor workers. Longhurst & Howse (1979a) reviewed the literature on Megaponera foraging behavior and found significant regional variation in how raids are conducted. Taylor (2008) hints that this variation supports his hypothesis of multiple species within Megaponera.

Hölldobler & Wilson (1990; see also Wilson, 1958a) hypothesized that the Megaponera style of foraging, in which scouts lead columns of workers on raids of other social insects, could be the first step in the evolution of true legionary behavior, such as that of the dorylines (see also Oster & Wilson, 1978). Of the hallmarks of legionary behavior identified by Brady (2003), Megaponera exhibits obligate collective foraging and a weak form of nomadism, by which colonies frequently emigrate to new nest sites. This latter behavior was described in detail by Arnold (reprinted in Wheeler, 1922b) and Longhurst & Howse (1979a). Wheeler (1922b) also discussed the adaptations of Megaponera brood to emigration. The reasons for these frequent emigrations are unknown, but Longhurst & Howse (1979a) argue that they are not likely caused by prey shortages and may be a response to predation by Dorylus driver ants. In an interesting observation, Beck & Kunz (2007) found cooperative altruistic defensive actions among Megaponera workers under attack by Dorylus.

Castes

Queens are ergatoid (permanently wingless) and have 64 ovarioles in the ovaries, which is exceptionally high among Ponerinae. Workers are polymorphic in size, and the largest workers have 24-30 ovarioles (Peeters 1991).

Nomenclature

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

  • MEGAPONERA [Ponerinae: Ponerini]
    • Megaponera Mayr, 1862: 734. Type-species: Formica foetens (junior primary homonym in Formica, replaced by Formica analis), by monotypy.
    • Megaponera junior synonym of Pachycondyla: Brown, in Bolton, 1994: 164.
    • Megaponera revived from synonymy: Schmidt & Shattuck, 2014: 104.
    • [Megaloponera: incorrect subsequent spelling by Roger, 1863b: 17; repeated by several authors, for example Emery, 1877b: 368; Forel, 1917: 237.]

Schmidt and Shattuck (2014):

Worker

Large to very large (TL 9–18 mm) ants with the standard characters of Ponerini. Workers polymorphic, varying principally in size and pubescence. Mandibles triangular. Eyes large, located near head midline, with distinct preocular carinae. Frontal lobes widely separated anteriorly and appearing flattened in frontal view. Scapes flattened, with distinct anterior margins. Metanotal groove shallow. Propodeum moderately narrowed dorsally. Propodeal spiracles slit-shaped. Tarsal claws with a preapical tooth. Metatibial spur formula (1s, 1p). Petiole nodiform. Constriction between pre- and postsclerites of A4 indistinct. Stridulitrum present on pretergite of A4. Head and body finely punctate, with scattered pilosity and dense pubescence (sparse in minor workers). Color black.

Queen

Wingless, similar to a major worker but larger (TL 18.5 mm), with more extensive sculpturing, denser pilosity, a deeper metanotal groove, an anteriorly slanting squamiform petiole, and a more expansive gaster. (Adapted from Arnold, 1915.)

Male

See descriptions in Emery (1897b), Arnold (1915), and Wheeler (1922b).

Larva

Described by Wheeler & Wheeler (1952).

References

  • Arnold, G. 1915. A monograph of the Formicidae of South Africa. Part I. Ponerinae, Dorylinae. Ann. S. Afr. Mus. 14: 1-159 (page 46, Megaponera in Ponerinae, Ponerini)
  • Ashmead, W. H. 1905c. A skeleton of a new arrangement of the families, subfamilies, tribes and genera of the ants, or the superfamily Formicoidea. Can. Entomol. 37: 381-384 (page 382, Megaponera in Pachycondylinae, Ectatommini)
  • Bolton, B. 1994. Identification guide to the ant genera of the world. Cambridge, Mass.: Harvard University Press, 222 pp. (page 164, Megaponera as junior synonym of Pachycondyla)
  • Bolton, B. 2003. Synopsis and Classification of Formicidae. Mem. Am. Entomol. Inst. 71: 370pp (page 166, Megaponera as junior synonym of Pachycondyla)
  • Dalla Torre, K. W. von. 1893. Catalogus Hymenopterorum hucusque descriptorum systematicus et synonymicus. Vol. 7. Formicidae (Heterogyna). Leipzig: W. Engelmann, 289 pp. (page 30, Megaponera in Ponerinae)
  • Emery, C. 1895l. Die Gattung Dorylus Fab. und die systematische Eintheilung der Formiciden. Zool. Jahrb. Abt. Syst. Geogr. Biol. Tiere 8: 685-778 (page 767, Megaponera in Ponerinae, Ponerini)
  • Emery, C. 1911e. Hymenoptera. Fam. Formicidae. Subfam. Ponerinae. Genera Insectorum 118: 1-125 (page 67, Megaponera in Ponerinae, Ponerini [subtribe Pachycondylini])
  • Mayr, G. 1862. Myrmecologische Studien. Verh. K-K. Zool.-Bot. Ges. Wien 12: 649-776 (page 714, Megaponera; (diagnosis in key) as genus; Megaponera in Ponerinae [Poneridae])
  • Mayr, G. 1865. Formicidae. In: Reise der Österreichischen Fregatte "Novara" um die Erde in den Jahren 1857, 1858, 1859. Zoologischer Theil. Bd. II. Abt. 1. Wien: K. Gerold's Sohn, 119 pp. (page 15, Megaponera in Ponerinae [Poneridae])
  • Schmidt, C.A. & Shattuck, S.O. 2014. The higher classification of the ant subfamily Ponerinae (Hymenoptera: Formicidae), with a review of ponerine ecology and behavior. Zootaxa. 3817, 1–242 (doi:10.11646/zootaxa.3817.1.1)
  • Wheeler, W. M. 1910b. Ants: their structure, development and behavior. New York: Columbia University Press, xxv + 663 pp. (page 135, Megaponera in Ponerinae, Ponerini)
  • 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 647, Megaponera in Ponerinae, Ponerini)