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Cyphomyrmex is a genus of small attines that occurs from the southern United States to Argentina. The main distinguishing feature of the genus is the broadly expanded frontal carinae. The most common species in the genus have the frontal carinae so flattened and broadened that they extend beyond the inner margins of the eyes, but a few less conspicuous species have the frontal carinae more narrow. All species have an at least partially formed antennal scrobe posterior to the eyes and extending to the vertex margin. The species have a relatively uniform habitus: they lack conspicuous erect setae or sharp spines, and they have a clean, smooth look. They have a mat surface and are never shiny. In Costa Rica the most difficult genus to distinguish from Cyphomyrmex is Mycetosoritis. Mycetosoritis (at least the one known Costa Rican species) has no development of an antennal scrobe posterior to the eyes, and the ant appears slightly "scruffy" with short suberect fine hairs in places.
The only major synthetic revision of the genus was and still is two papers by Kempf (1964, 1966). A few subsequent species descriptions have been added by Kempf (1968), MacKay and Baena (1993), and Schultz et al. (2002). Snelling and Longino (1992) attempted to revise the rimosus complex. In my opinion this was only moderately successful.
In much of the Neotropics these are among the most abundant attines in the habitat, but they are always inconspicuous ants. They have small colonies, with worker numbers usually in the tens to hundreds. The nests are usually in small chambers in the ground, under objects, or in rotten wood. Some of the less common species have more interesting nest structure. Cyphomyrmex cornutus makes a large exposed nest of accreted organic material suspended from vines, small branches, or the undersurfaces of tree trunks. Cyphomyrmex cf. longiscapus and C. cf. muelleri make nests in vertical clay banks or beneath horizontal dead tree trunks, and they use accreted soil or organic matter to construct elaborate flaring or "auriculate" nest entrances (Mueller and Wcislo 1998, Schultz et al. 2002).
Within the genus there is a transition in fungus gardens from a mycelial to a yeast growth form. Some of the primitive members of the genus have the white spongy fungus gardens typical of other attines, but the more derived species (and by far the most common) have the garden substrate covered with pale cream colored to slightly greenish dots, a yeast form of the fungus. There is renewed interest in the coevolution and chemical ecology of attines and their fungi, and several papers have explored Cyphomyrmex in particular (Mueller et al. 1996, Murakami and Higashi 1997, Nair and Hervey 1979, Wang et al. 1999).
The main fungal substrates used by the common Cyphomyrmex are caterpillar droppings and dead insect parts. The insect parts are mainly heavily sclerotized bits of exoskeleton, and brightly colored beetle elytra seem to be particularly favored. When a small Cyphmyrmex colony is exposed by turning over a leaf on the forest floor or breaking into a small cavity in a rotten log, one is faced with an almost magical little scene: one or two large caterpillar pellets form the center of the fungus garden, embedded in a glittering, multicolored pile of beetle elytra, membracid pronota, and miscellaneous leg parts, and all covered with the little green fungal dots. The workers tuck their legs and become motionless on disturbance, entering a "cateleptic" state, and so at first the small brown workers are an invisible part of the background in and around the fungus garden. After a few minutes, if left undisturbed, one by one the workers appear to suddenly spring into motion.
Kempf, W. W. 1964. A revision of the Neotropical fungus-growing ants of the genus Cyphomyrmex Mayr. Part I: Group of strigatus Mayr (Hym., Formicidae). Studia Entomologica 7:1-44.
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.
Kempf, W. W. 1968. A new species of Cyphomyrmex from Colombia, with further remarks on the genus (Hymenoptera, Formicidae). Rev. Brasil. Biol. 28:35-41.
MacKay, W. P., and M. L. Baena. 1993. A new "horned" fungus growing ant, Cyphomyrmex castagnei, from Colombia. Sociobiology 23:31-37.
Mueller, U. G., S. E. Lipari, and M. G. Milgroom. 1996. Amplified fragment length polymorphism (AFLP) fingerprinting of symbiotic fungi cultured by the fungus-growing ant Cyphomyrmex minutus. Molecular Ecology 5:119-122.
Mueller, U. G., and W. T. Wcislo. 1998. Nesting biology of the fungus-growing ant Cyphomyrmex longiscapus Weber (Attini, Formicidae). Insectes Sociaux 45:181-189.
Murakami, T., and S. Higashi. 1997. Social organization in two primitive attine ants, Cyphomyrmex rimosus and Myrmicocrypta ednaella, with reference to their fungus substrates and food sources. Journal of Ethology 15:17-25.
Nair, M. S. R., and A. Hervey. 1979. Structure of lepiochlorin, an antibiotic metabolite of a fungus Lepiota species cultivated by ants Cyphomyrmex costatus. Phytochemistry 18:326-327.
Schultz, T. R., S. A. Solomon, U. G. Mueller, P. Villesen, J. J. Boomsma, R. M. M. Adams, and B. Norden. 2002. Cryptic speciation in the fungus-growing ants Cyphomyrmex longiscapus Weber and Cyphomyrmex muelleri Schultz and Solomon, new species (Formicidae, Attini). Insectes Sociaux 49:331-343.
Snelling, R. R., and J. T. Longino. 1992. Revisionary notes on the fungus-growing ants of the genus Cyphomyrmex, rimosus group (Hymenoptera: Formicidae: Attini). Pages 479-494 in D. Quintero and A. Aiello, editors. Insects of Panama and Mesoamerica: selected studies. Oxford University Press, Oxford. xxii + 692 p.
Wang, Y., U. G. Mueller, and J. Glardy. 1999. Antifungal diketopiperazines from symbiotic fungus of fungus-growing ant Cyphomyrmex minutus. J. Chem. Soc. 25:935-941.
John T. Longino, The Evergreen State College, Olympia WA 98505 USA.email@example.com
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