Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
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Image of ergatoid queen: (large image, small image).
Identification
Dorsal and lateral faces of femora with abundant erect setae; mesepisternum with ten or more erect setae scattered over surface
Similar species: A. araneoides.
Range
Costa Rica (type loc.), Panama. Costa Rica: southern Pacific lowlands and cordilleras (distribution map: small, large).
Natural History
This species occurs in wet to moist forest habitats, from sea level to 1400m montane forest (Longino and Cover 2004). Workers are solitary foragers on the forest floor, where they are generalized omnivores, scavengers, and predators on small arthropods. They regularly come to baits of all kinds. Nests are subterranean with an inconspicuous entrance at the soil surface. McGlynn et al. (2002, 2003) studied the biology of the closely related A. araneoides. They found that colonies regularly maintain multiple empty nests, moving among them. Mean colony size was 123 workers (range 55-235). They also found that colonies lacked normal alate queens and instead had ergatoid queens. Colonies usually had one and rarely two ergatoid queens. The biology of A. phalangium is probably very similar. Alate queens are unknown in the species complex, and two excavated colonies of A. phalangium have had ergatoid queens (Longino and Cover 2004).
Longino twice observed the following phenomenon, once in Corcovado National Park with A. phalangium, and once at La Selva Biological Station with A. araneoides. During night collecting, he shined a light on a nest entrance. Workers immediately rushed out of the entrance, each carrying a larva. They ran a few cm from the nest entrance and stopped, then slowly returned to the nest. The exodus from the nest was so rapid that the workers must have been near the nest entrance, already with larvae. It was as though they were waiting at the entrance, ready for a panic evacuation, and set on a hair trigger, such that the smallest stimulus would send them out.
Taxonomy
Aphaenogaster phalangium Emery 1890:47, pl. 5, fig. 6, 7. Lectotype worker: Costa Rica [worker probably from Alajuela] (Alfaro) [MCSN] (examined). Also described as new by Emery 1894:54. Description of larva (as A. araneoides inermis Forel): Wheeler and Wheeler 1953:64. Combination in Aphaenogaster (Ischnomyrmex): Forel 1899:59; in Aphaenogaster (Deromyrma): Emery 1915:71.
Aphaenogaster (Ischnomyrmex) araneoides var. inermis Forel 1899:60. Lectotype worker: Costa Rica (Tonduz) [MHNG] (examined). Combination in Aphaenogaster (Deromyrma): Kempf 1972:23. Synonym of A. phalangium: Longino and Cover 2004:10. Images of lectotype: click here.
Aphaenogaster (Ischnomyrmex) araneoides var. nitidiventris Forel 1912:15. Syntype worker, male: Costa Rica, Ca–as Gudas [sic, Ca–as Gordas] (Pittier) [MHNG] (examined). Combination in Aphaenogaster (Deromyrma): Kempf 1972:23. Synonym of A. phalangium: Longino and Cover 2004:10. Images of syntypes: click here.
Aphaenogaster (Deromyrma) araneoides var. canalis Enzmann, J. 1947:149, pl. 8. worker: Panama. Synonym of A. phalangium: Longino and Cover 2004:10.
See under A. araneoides for discussion of A. phalangium lectotype designation.
The A. inermis syntypes that were collected by Tonduz in Costa Rica are identical to material from Corcovado National Park, with matte gaster and strongly constricted neck. The Wheelers' (1953) description of the larva of A. inermis was based on material from Barro Colorado Island in Panama. The A. nitidiventris syntypes were collected in Ca–as Gordas, a site on the border with Panama in the Cordillera de Talamanca. They match more recent collections of A. phalangium from this area. They have a highly constricted neck, like material from the nearby Pacific lowlands, but the fourth abdominal tergite is sublucid and weakly shagreened. The identity of Enzmann's A. canalis cannot be unambiguously determined from the description or figure, but the description states "The insect is covered with beautiful golden erect hairs, which are longer and more abundant on the vertex and gaster, shorter and sparser on the thorax and legs." The fact that setae were mentioned on the legs suggests A. phalangium. Types were from Chiriqui, Panama, which, if from the lowlands, would be expected to be A. phalangium.
Literature Cited
Emery, C. (1890) Studii sulle formiche della fauna neotropica. Bullettino della Societˆ Entomologica Italiana 22, 38-80.
Emery, C. (1894) Estudios sobre las hormigas de Costa Rica. Anales del Museo Nacional de Costa Rica 1888-1889, 45-64.
Emery, C. (1915) Definizione del genere Aphaenogaster e partizione di esso in sottogeneri. Parapheidole e Novomessor nn. gg. Rendiconti delle Sessioni della Reale Accademia delle Scienze dell'Istituto di Bologna. Classe di Scienze Fisiche (n.s.) 19, 67-75.
Enzmann, J. (1947) New forms of Aphaenogaster and Novomessor. Journal of the New York Entomological Society 55, 147-152.
Forel, A. (1899) Formicidae. [part]. Biologia Centrali-Americana 3, 57-80.
Forel, A. (1912) Formicides nŽotropiques. Part IV. 3me sous-famille Myrmicinae Lep. (suite). MŽmoires de la SociŽtŽ Entomologique de Belgique 20, 1-32.
Kempf, W. W. (1972) Cat‡logo abreviado das formigas da regia~o Neotropical. Studia Entomologica 15, 3-344.
Longino, J. T., and S. Cover. 2004. A Revision of the Aphaenogaster phalangium complex (Hymenoptera: Formicidae: Myrmicinae). Zootaxa 655:1-12.
McGlynn, T. P., Hoover, J. R., Jasper, G. S., Kelly, M. S., Polis, A. M., Spangler, C. M., and Watson, B. J. (2002) Resource heterogeneity affects demography of the Costa Rican ant Aphaenogaster araneoides. Journal of Tropical Ecology 18, 231-244.
McGlynn, T. P., Shotell, M. D., and Kelly, M. S. (2003) Responding to a variable environment: Home range, foraging behavior, and nest relocation in the Costa Rican rainforest ant Aphaenogaster araneoides. Journal of Insect Behavior 16, 687-701.
Wheeler, G. C., Wheeler, J. (1953) The ant larvae of the myrmicine tribe Pheidolini (Hymenoptera, Formicidae). Proceedings of the Entomological Society of Washington 55, 49-84.
Page authors:
John T. Longino, The Evergreen State College, Olympia WA 98505 USA. longinoj@evergreen.edu
Stefan Cover, Museum of Comparative Zoology, Harvard University, Cambridge MA 02138 USA. scover@oeb.harvard.edu
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