Megalomyrmex wettereri Brandao 2003

Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia

Identification

Mandibles with large apical tooth, smaller subapical tooth, and 5-6 smaller denticles of more or less uniform size; mandibles shiny with large piligerous punctures; clypeus broadly and evenly convex; eyes small, 4-5 facets in maximum diameter; occipital carina not visible in face view; propodeal suture moderately impressed; dorsal and posterior faces of propodeum distinct; propodeum with longitudinal median depression; epipetiolar carina incomplete; petiole with anteroventral tooth that is laterally compressed, not a transverse flange; postpetiole with small anteroventral tooth; color yellow; HW 0.50; HL 0.60, SL 0.49; WL 0.83 (n=1).

Range

Costa Rica, Panama. In Costa Rica, known only from La Selva.

Natural History

The Costa Rican specimens of the new species were collected by Jim Wetterer. While collecting Attini at La Selva Biological Station, he discovered a colony occupying the fungus garden of a Trachymyrmex nest. Several other species of Megalomyrmex, including mondabora, silvestrii, and symmetochus, appear to be specialized associates or predators of small attines (Wheeler 1925, Kempf and Brown 1968, Brandao 1990, Adams et al. 2000). Adams et al. describe in detail the behavior of this species. I quote from Brandão's (2003) summary of their findings:

Adams et al. (1998-1999; 2000) described the finding of two colonies of this new species in Panama containing healthy fungus gardens of Cyphomyrmex longiscapus, although no attines were present at the time of collecting. According to these authors, laboratory observations revealed that the Megalomyrmex “consume the fungus by cropping mycelium from the garden substrate. However, they do not forage for and add nutrient substrates, or otherwise tend the fungus garden; thus, when the garden becomes depleted, Megalomyrmex sp. must locate and usurp new gardens in other attine colonies”. When presented with active colonies of C. longiscapus, workers of this new species displace “host” workers in mass raids, stinging and ultimately killing the apparent defenseless C. longiscapus. When presented with C. longiscapus larvae in the laboratory, M. wettereri n. sp. workers strip them of the mycelium layer that naturally covers the cuticle, then place the larvae with their own brood. Adams et al. (1998-1999) considered this Megalomyrmex as a predator on C. longiscapus as they forcibly eject the resident attine to usurp their fungus gardens.

Literature Cited

Adams, R.C., Mueller, U.G. and Schultz, T.R. 1998-1999. Nest usurpation and fungivory in Megalomyrmex sp. nov. (Silvestrii species group): lestobiotic or predatory relations with fungus growing ants? In: Schwarz, M.P. and Hogendoorn (eds.) Insects at the Turn of the Millennium, International Congress of IUSSI, 14th. Proceedings. Adelaide, Australia, IUSSI. p.75.

Adams, R. M. M., U. G. Mueller, T. R. Schultz, and B. Norden. 2000. Agro-predation: usurpation of attine fungus gardens by Megalomyrmex ants. Naturwissenschaften 87:549-554.

Brandão, C. R. F. 1990. Systematic revision of the Neotropical ant genus Megalomyrmex Forel (Hymenoptera: Formicidae: Myrmicinae), with the description of thirteen new species. Arquivos de Zoologia (Sao Paulo) 31:411-481.

Brandão, C. R. F. 2003. Further revisionary studies on the ant genus Megalomyrmex Forel (Hymenoptera: Formicidae: Myrmicinae: Solenopsidini. Papéis Avulsos de Zoologia 43:145-159.

Kempf, W. W., Brown, W. L., Jr. 1968. Report on some Neotropical ant studies. Papeis Avulsos Zool. 22:89-102.

Wheeler, W. M. 1925. A new guest-ant and other new Formicidae from Barro Colorado Island, Panama. Biol. Bull. Mar. Biol. Lab., Woods Hole 49:150-181.

Page author:

John T. Longino, The Evergreen State College, Olympia WA 98505 USA. longinoj@evergreen.edu

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