Megalomyrmex is a genus of ant in the subfamily Myrmicinae. The genus is known only from the Neotropics, where some of the species are specialized parasites or predators of Attini.
Description
It is difficult to characterize morphologically. Bolton (2003) placed it in the tribe Solenopsidini, but with multiple exceptions to the diagnostic characters for the tribe. The tribal characters include a bicarinate clypeus and a median clypeal seta. Most Megalomyrmex species have a smoothly convex clypeus with no trace of the bicarinate condition, and most have abundant clypeal setae with no distinct or differentiated median seta. In Bolton's (1994) key to genera, Megalomyrmex keys in multiple places because of variability in mandibular dentition. Nevertheless, the genus has a distinctive habitus: the antenna is 12-segmented with a 3-segmented club; the general integument is smooth and shiny without coarse sculpture or dull areas; the promesonotum is evenly arched, without promesonotal groove; the propodeum is usually smoothly curved between dorsal and posterior faces, at most with blunt, broad-based tubercles, and never with spines; and the hind tibial spur is simple. In short, the workers look like a Solenopsis with Pheidole antennae. The mandibular dentition varies from a simple set of 5 similar teeth on the masticatory margin, gradually diminishing in size basally, to a condition with 2 large apical teeth followed by up to 12 small denticles.
Some species have unusual alkaloids. The hypothesis that alkaloids act at a distance converges with what is known for the genera Solenopsis, Monomorium and Megalomyrmex when workers release volatile venom alkaloids by waving their stingers (i.e., gaster flagging) during interspecific encounters causing their enemies to flee.
Distribution and habitat Although widespread in the Neotropics, from southern Mexico to northern Argentina, Megalomyrmex species are never abundant. They occur in low to middle elevation wet to dry forest habitats. Some species are free-living with large diffuse nests in the soil (e.g. Megalomyrmex modestus) or small nests in dead wood (e.g. Megalomyrmex drifti). Others are specialized social parasites or predators of Attini (e.g. Megalomyrmex adamsae, Megalomyrmex mondabora, Megalomyrmex symmetochus, Megalomyrmex wettereri).
Species Extant
Megalomyrmex acauna Brandão, 1990 Megalomyrmex adamsae Longino, 2010 Megalomyrmex ayri Brandão, 1990 Megalomyrmex balzani Emery, 1894 Megalomyrmex bidentatus Fernández & Baena, 1997 Megalomyrmex brandaoi Boudinot et al., 2013 Megalomyrmex caete Brandão, 1990 Megalomyrmex cuatiara Brandão, 1990 Megalomyrmex cupecuara Brandão, 1990 Megalomyrmex cyendyra Brandão, 1990 Megalomyrmex drifti Kempf, 1961 Megalomyrmex emeryi Forel, 1904 Megalomyrmex foreli Emery, 1890 Megalomyrmex fungiraptor Boudinot et al., 2013 Megalomyrmex glaesarius Kempf, 1970 Megalomyrmex gnomus Kempf, 1970 Megalomyrmex goeldii Forel, 1912 Megalomyrmex iheringi Forel, 1911 Megalomyrmex incisus Smith, 1947 Megalomyrmex leoninus Forel, 1885 Megalomyrmex longinoi Boudinot et al., 2013 Megalomyrmex megadrifti Boudinot et al., 2013 Megalomyrmex milenae Boudinot et al., 2013 Megalomyrmex miri Brandão, 1990 Megalomyrmex modestus Emery, 1896 Megalomyrmex mondabora Brandão, 1990 Megalomyrmex mondaboroides Longino, 2010 Megalomyrmex myops Santschi, 1925 Megalomyrmex nocarina Longino, 2010 Megalomyrmex osadrifti Boudinot et al., 2013 Megalomyrmex pacova Brandão, 1990 Megalomyrmex peetersi do Prado & Adams, 2020 Megalomyrmex piriana Brandão, 1990 Megalomyrmex poatan Brandão, 1990 Megalomyrmex pusillus Forel, 1912 Megalomyrmex reina Longino, 2010 Megalomyrmex silvestrii Wheeler, 1909 Megalomyrmex staudingeri Emery, 1890 Megalomyrmex symmetochus Wheeler, 1925 Megalomyrmex tasyba Brandão, 1990 Megalomyrmex timbira Brandão, 1990 Megalomyrmex wallacei Mann, 1916 Megalomyrmex wettereri Brandão, 2003 Megalomyrmex weyrauchi Kempf, 1970
Unidentifiable One species tentatively placed within the genus has subsequently been determined as unidentifiable to the species level due to various reasons like loss of or extensive damage to the type specimen, a description deemed too vague to identify to the species level, or often both simultaneously, although it technically remains a valid binomen. Megalomyrmex bituberculatus (Fabricius, 1798)
References
Bolton, B. (1994) Identification Guide to the Ant Genera of the World. Harvard University Press, Cambridge, MA, London, 222 pp. Bolton, B. (2003) Synopsis and classification of Formicidae. Memoirs of the American Entomological Institute 71: 1–370
External links