Subfamily MYRMICINAE
Tribe ATTINI

Cyphomyrmex rimosus (Spinola) 1851

by Joe A. MacGown, last updated 26 November 2013

Cyphomyrmex rimosus, frontal view of the head of a worker (photo by Joe A. MacGown)
Cyphomyrmex rimosus, side view of a worker (photo by Joe A. Macgown)
Cyphomyrmex rimosus, side view of a queen (photo by Joe A. MacGown)

Introduction
Cyphomyrmex is in the Attini tribe and is related to Atta and Trachymyrmex, which are also found in the southern United States.

Cyphomyrmex rimosus is a small dull brown to blackish brown attine ant with deep antennal scrobes, enlarged frontal lobes that obscure the lateral margins of the face (see photo of head above), no propodeal spines, an apedunculate petiole, and tubercles on the mesosoma.  The species is native to the Neotropics, but has established introduced populations in the southern United States and the Galapagos islands. It is not considered a pest species in its native or introduced range.

Taxonomic History (provided by Barry Bolton, 2013)
Cryptocerus rimosus Spinola (1851); also described as new by Spinola (1853); Combination in Cyphomyrmex, Emery (1893); in Atta (Cyphomyrmex), Forel (1912); in Cyphomyrmex, Bruch  (1914). Senior synonym of Cyphomyrmex difformis, Forel (1893); Emery (1894); of Cyphomyrmex cochunae, Cyphomyrmex fuscus (and its junior synonyms Cyphomyrmex curiapensis, Cyphomyrmex fuscula), Snelling and Longino (1992).

Identification
Relatively small (head width greater than 0.62 mm) monomorphic ants that vary in color from dull light brown to blackish brown. The frontal lobes are conspicuous and expanded laterally and cover the antennal bases as well as much of the front of the head (see photo above, frontal view). The eyes are well developed. Mandibles with five teeth. Antennae 11- merous, with a 2-segmented club. Body is strongly sculptured with rounded tubercles present on the dorsum of the alitrunk (see photo of side view of worker above). Numerous appressed, scale-like hairs present on the body and appendages.

This species is similar to C. minutus, which is apparently native to Florida and smaller in size. According to Snelling and Longino (1992), the head width of C. minutus is less than 0.56 mm and hairs in center of first gastral tergite are closely appressed and usually separated by more than their own lengths, whereas in C. rimosus, the head width is greater than 0.62 mm and hairs on first gastral tergite are not completely appressed and separated by less than their own lengths (Snelling and Longino 1992). I examined specimens of both species at the collection in Gainesville, FL and had a hard time telling them apart, but I did not have an ocular micrometer to measure head widths.

Common Names
Fungus growing ant

Biology and Economic Importance
Cyphomyrmex rimosus is part of a complex of closely related and highly variable taxa that can be difficult to distinguish (Kempf, 1966 (1965)). The C. rimosus group was split it into five subgroups by Snelling and Longino (1992) and now contains seven species, including C. rimosus and the closely related C. minutus. Both of these species occur in Florida. However, based on its rapid spread after initially being detected, C. rimosus is thought to be introduced; whereas, Cyphomyrmex minutus is considered native (Deyrup, 1991). Prior to the revision by Snelling and Longino (1992), Cyphomyrmex minutus was treated as a junior synonym of C. rimosus. This makes it difficult to know exactly which species earlier studies referred to. Snelling & Longino (1992) state that many of the Neotropical and North American records in the literature may actually refer to the more widespread C. minutus.

The colony size of C. rimosus is typically small, with usually less than 100 workers, although colonies with over 300 workers have been observed (Murakami & Higashi, 1997). Ccolonies are typically monogynous, but may be polygynous (Murakami and Higashi, 1997; Snelling and Longino, 1992).

Similar to other Attines, Cyphomyrmex cultivates subterranean fungus gardens, growing the fungus on a substrate of vegetable matter, insect frass, and dead insects. These fungus gardens are composed of yeasts in the unicellular phase. Fungal gardens of most other attine species are in the multicellular, mycelial phase (Mehdiabadi & Schultz, 2010).  Cyphomyrmex rimosus supplements its diet with nectar and sap of plants (Murakami & Higashi, 1997). The queens have been reported to practice monandry and semi-claustral nest founding (Mehdiabadi & Schultz, 2010; Tschinkel, 1987). Nests are often simple, shallow, impermanent structures under rocks, logs, dry cow manure, or any other surface. This species is very common in open habitats such as pastures and also in open woodlands such as longleaf pine forests.

This species is not considered to be a pest, but in areas of high abundance, they could invade homes in search of sugary food substances.

Distribution
Native Range: Neotropics. Argentina, Brazil, Guinanas, Venezuala (Snelling and Longino, 1992). .

Introduced Range (non US). Galapagos: Isabella, Santa Cruz (Snelling and Longino, 1992).

Introduced Range in the United States: Alabama, Florida, Georgia, Mississippi, and Texas (MEM). Smith (1979) also reported this species from Arizona and California, but Snelling and Longino (1992) did not include it as occurring in those states in their more recent publication. Thus, these records are likely incorrect.

Literature Cited
Bolton, B. 2013.  Bolton World Catalog Ants. Available online: http://www.antweb.org/world.jsp. Accessed 16 April 2013.

Bruch, C. 1914. Catálogo sistemático de los formícidos argentinos. Revista del Museo de La Plata 19: 211-234.

Deyrup, M. 1991. Exotic ants of the Florida keys (Hymenoptera: Formicidae). In: Eshbaugh, W.H. (Ed.) Proceedings of the 4th symposium on the natural history of the Bahamas. Bahamian Field Station, San Salvador, Bahamas, pp. 15-22.

Emery, C. 1893. Intorno ad alcune formiche della collezione Spinola. Bollettino dei Musei di Zoologia ed Anatomia Comparata della Reale Università di Torino 8(163): 1-3. 

Emery, C. 1894. Studi sulle formiche della fauna neotropica. VI-XVI. Bullettino della Società Entomologica Italiana 26: 137-241. 

Forel, A. 1893. Note sur les Attini. Annales de la Société Entomologique de Belgique 37: 586-607. 

Forel, A. 1912. Formicides néotropiques. Part II. 3me sous-famille Myrmicinae Lep. (Attini, Dacetii, Cryptocerini). Mémoires de la Société Entomologique de Belgique 19: 179-209.

Mehdiabadi, N. J. and R. Schultz. 2010. Natural history and phylogeny of the fungus-farming ants (Hymenoptera: Formicidae: Myrmicinae: Attini). Myrmecol. News, 13: 37-55.

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. J. Ethol., 15, 17-25.

Kempf, W.W. (1966 (1965)) A revision of the Neotropical fungus-growing ants of the genus Cyphomyrmex Mayr. Part II: Group ofrimosus (Spinola) (Hym., Formicidae). Stud. Entomol., 8: 161-200.

Smith, D. R. 1979. In Catalog of Hymenoptera in America north of Mexico. Smithsonian Institution Press, Washington D. C. Vol. 2, pp. 1323-1427.

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 Quintero, D. and A. Aiello. Insects of Panama and Mesoamerica: selected studies. Oxford University Press, Oxford. 692 pp.

Spinola, M. 1851. Compte rendu des Hyménoptères inédits provenants du voyage entomologique de M. Ghiliani dans le Para en 1846. Extrait des Mémoires de l'Académie des Sciences de Turin (2)13: 3-78.

Spinola, M. 1853. Compte rendu des Hyménoptères inédits provenants du voyage entomologique de M. Ghiliani dans le Para en 1846. Memorie della Reale Accademia delle Scienze di Torino (2)13: 19-94. 

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