Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
Mexico south to northern South America, extending to southwestern Ecuador to the west and the guianas to the east, but barely entering the Amazon basin in northern Brazil (Kugler and Brown 1982). Costa Rica: widespread in lowlands; absent from Osa Peninsula (its absence from the Osa is peculiar, given its ubiquity elsewhere).
Pronotum with a well-differentiated median eminence and a pair of dorsolateral (humeral) teeth; petiolar node as seen from the side high and thin, at least the upper half with anterior and posterior faces vertical and subparallel; head in perfect full-face view with posterior outline transverse, nearly stright over most of the distance between eyes; color reddish brown to nearly black.
Ectatomma ruidum is one of the most common ants in Costa Rica. It occurs in both wet forest and dry forest habitats. Nests are below ground and may reach high densities in open areas (Weber 1946, Lachaud 1990). The nest entrance is an unadorned and inconspicuous hole in the ground, the hole little larger in diameter than a worker. Workers forage on the ground surface and on low vegetation. They are predators, generalized scavengers, and avid collectors of extrafloral nectar. Colonies may be polygynous: Weber observed a colony in Colombia with 13 dealate queens and at least 24 workers. Weber also observed in a lab colony that a worker developed a swollen gaster and began laying eggs after the queen died. It is not clear whether the eggs were viable.
Workers recruit nestmates to food sources (Lachaud 1985, Pratt 1989), and they use a trail pheromone produced from the Dufour's gland (Bestmann et al. 1995). They do not exhibit a strong trail following response to the trail pheromone unless first incited by returning scout ants (Pratt 1989, Bestmann et al. 1995). Workers may engage in cleptobiosis, detecting the foraging trails of other ant species and stealing food from returning foragers (Perfecto and Vandermeer 1993). Workers may feign death when disturbed (Cupul-Maga–a 2009).
Ponera (Ectatomma) ruida Roger 1861:306. Syntype worker, queen: "Colombia". Type locality chosen by Kugler and Brown 1982; other original localities were "Brasil" and "Cayenne."
Bestmann, H. J., E. Janssen, F. Kern, B. Liepold, and B. Hoelldobler. 1995. All-trans Geranylgeranyl acetate and geranylgeraniol, recruitment pheromone components in the dufour gland of the ponerine ant Ectatomma ruidum. Naturwissenschaften 82:334-336.
Breed, M. D., P. Abel, T. J. Bleuze, and S. E. Denton. 1990. Thievery, home ranges and nestmate recognition in Ectatomma ruidum. Oecologia 84:117-121.
Cupul-Maga–a, F. G.. 2009. Primera observaci—n del comportamiento defensivo por muerte simulada de la hormiga Ectatomma ruidum (roger, 1861) (Formicidae, Ponerinae). Acta Zool—gica Mexicana (n.s.) 25: 199-201.
Jaffe, K., and M. Marquez. 1987. On agonistic behavior among workers of the ponerine ant Ectatomma ruidum (Hymenoptera Formicidae). Insectes Soc. 34:87-95.
Kugler, C., W. L. Brown, Jr. 1982. Revisionary and other studies on the ant genus Ectatomma, including the descriptions of two new species. Search: Agriculture (Cornell), No. 24, 8 pp.
Lachaud, J. P. 1985. Recruitment by selective activation: an archaic type of mass recruitment in a ponerine ant (Ectatomma ruidum). Sociobiology 11:133-142.
Lachaud, J. P. 1990. Foraging activity and diet in some neotropical ponerine ants I. Ectatomma ruidum Roger (Hymenoptera Formicidae). Folia Entomol. Mexicana (78):241-256.
Perfecto, I., and J. H. Vandermeer. 1993. Cleptobiosis in the ant Ectatomma ruidum in Nicaragua. Insectes Sociaux 40:295-299.
Pratt, S. C. 1989. Recruitment and other communication behavior in the ponerine ant Ectatomma ruidum. Ethology 81:313-331.
Roger, J. 1861(1860). Die Ponera-artigen Ameisen I. Berl. Entomol. Z. 4:278-312.
Weber, N. A. 1946. Two common ponerine ants of possible economic significance, Ectatomma tuberculatum (Olivier) and E. ruidum Roger. Proc. Entomol. Soc. Wash. 48:1-16.
John T. Longino, The Evergreen State College, Olympia WA 98505 USA.email@example.com
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