Attini, Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
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Additional images: dorsal view (large, small), gaster (large, small).
Range
Honduras (type locality), Costa Rica, Colombia, Venezuela. Costa Rica: lowland wet forests of Atlantic and Pacific slopes, below 500m elevation.
Identification
Disk of first gastral tergite with two prominent longitudinal carinae (unique among Costa Rican species).
Natural History
Cyphomyrmex costatus inhabits wet forest habitats. It forms small nests in the leaf litter and is most frequently encountered in Winkler samples of sifted leaf litter.
The following is from the bionomics section of Kempf (1966):
The types of the species were found by Mann in rotten wood. No further detail is given.The bulk of our information has been gathered by Weber, who, in successive studies (1941-57), was able to elucidate many aspects of its biology, so that in this regard costatus is one of the best known species of the genus.
Weber's observations were made in Panama, principally on Barro Colorado Island. There, the ants are not uncommon, although seasonal scarcity, due to dry seasons and different stages of the wet season, has been observed. The nests are found in the soil, under stones or rotten wood. The cells, elliptical in shape, are of variable size, according to colony development. 8X5, 15X10, 32X13 and 30x20 mm with a maximum height of 10 mm are the dimensions obtained by actual measurements in the field.
The fungus garden is bluish gray in color, friable, and crumbles easily. In nature, the garden, though sessile, is in part supported by rootlets. The substrate, consisting of vegetable debris, is strengthened by quartz sand grains, parts of insect skeletons, notably of ants (Weber gives a list of parts from a variety of species), forming the frame work of the fungus-garden.
In artifical cultures, the ants accepted as substrate dried fecal pellets of caterpillars, rose stamens, and cassava granules dusted with yeast extract. The material collected in Panama, in June 1955, was taken to the U. S. by Prof. Weber, who studied the factors responsible for the production and maintenance of thriving cultures of fungi in ant gardens, despite continual possibilities for contamination. The most striking result of this important research consisted in the development, from artifical cultures, of the sporophore or fruiting stage of the fungus cultivated by costatus. This was identified by two specialists as a new species belonging to the agaric genus Lepiota.
Individual colonies, always monogynous, may contain from 20 up to nearly 100 workers. Individual behavior, like "jigging" and grooming was likewise observed (ct. Weber, 1957: 484).
Finally, the ant Megalomyrmex wheeleri Weber was found living in symbiotic relationship with Cyphomyrmex costatus. The former, apparently feeding on the fungus, occurred in 4 nests of the latter. In two nests, there was only a queen of Megalomyrmex, in the remaining nests a queen with numerous workers of her own species. In all cases, the guests lived in a separate cell which, however, communicated with the cell containing the fungus garden. The host species did not disturb the guest. Due to adverse conditions, the study of this relationship could not be carried to completion.
Comments
Kempf (1966) described the queen and made C. colombianus a junior synonym. Wheeler (1949) described the larva (misidentified as strigatus).
Literature Cited
Kempf, W. W. 1966 ("1965"). A revision of the Neotropical fungus-growing ants of the genus Cyphomyrmex Mayr. Part II: Group of rimosus (Spinola) (Hym., Formicidae). Studia Entomologica 8:161-200.
Weber, N. A. 1940. The biology of the fungus-growing ants. Part VI. Key to Cyphomyrmex, new Attini and a new guest ant. Rev. Entomol. (Rio de Janeiro) 11:406-427.
Weber, N. A. 1941. The biology of the fungus-growing ants. Part VII. The Barro Colorado Island, Canal Zone, species. Rev. Entomol. (Rio de Janeiro) 12:93-130.
Weber, N. A. 1957. Dry season adaptations of fungus-growing ants and their fungi. Anatomical Record 128:638.
Weber, N. A. 1957. Fungus-growing ants and their fungi: Cyphomyrmex costatus. Ecology 38:480-494.
Weber, N. A. 1958 (1956). The fungus growing ant, Cyphomyrmex costatus, and the sporophore of its fungus. Proceedings of the X International Congress of Entomology 2: 723, Montreal.
Wheeler, G. C. 1949 ("1948"). The larvae of the fungus-growing ants. American Midland Naturalist 40:664-689.
Page author:
John T. Longino, The Evergreen State College, Olympia WA 98505 USA.longinoj@evergreen.edu
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