Cyphomyrmex rimosus

A tropical species, or complex of closely related species, that has been introduced to other areas from its native range in Central and South America.

Identification
Using published keys (Kempf 1966, Snelling and Longino 1992) some collections from some areas readily agree with published ideas of what constitutes the present set of valid species in this complex. In other cases individuals or nests series are difficult to determine to species, which in turn suggests our current understanding of the rimosus-species group needs a thorough taxonomic reevaluation. See the nomenclature section below for additional information.

Distribution
A common, introduced species found throughout Florida. It occurs in both undisturbed mesic or wet woods and various disturbed habitats. This species has only recently become abundant in northern Florida (where there are no early records) and is now sympatric with Cyphomyrmex minutus in southern Florida (Deyrup 1991). Pest status: none. First published Florida records: Deyrup and Trager 1986 (as C. fuscus Emery), Johnson 1986; earlier specimens: 1957. (Deyrup, Davis & Cover, 2000.)

Distribution based on Regional Taxon Lists
Nearctic Region: United States. Neotropical Region: Argentina, Belize, Bolivia, Brazil, Colombia, Costa Rica, Dominican Republic, Ecuador, French Guiana, Galapagos Islands, Greater Antilles, Guatemala, Guyana, Haiti, Lesser Antilles, Mexico, Nicaragua, Panama, Paraguay, Peru, Suriname, Trinidad and Tobago, Uruguay, Venezuela.

Biology
This species depends on fungi that it grows on compost beds of vegetable matter mixed with scavenged bits of dead insects; it does not cut pieces of leaves from living plants.

Brazil
Ramos-Lacau et al. (2015) found this species co-occurring with Cyphomyrmex lectus and Cyphomyrmex strigatus in savanna-forest in Southeast Brazil. Colonies were found nesting in the ground. Each nest had a single, simple circular nest-entrance. These averaged a few mm in diameter and did not have any well formed nest mound.

Costa Rica
Longino (2004) reports the following: This species, possibly a complex of cryptic species (see comments), occurs in a wide range of habitats, including dry open ground of synanthropic habitats, seasonal dry forest, and lowland rainforest. This is the most abundant species in open areas, replaced in abundance by Cyphomyrmex salvini in wet forest habitats. Nests are in the soil, under stones, or under dead wood on the ground. I have also found nests in subarboreal cavities, such as rotten knots in tree trunks and dead wood suspended in vegetation, but usually within 2m of the ground. Colonies can be polygynous; one nest I observed contained at least four dealate queens. Workers forage on the surface, harvesting small insect parts and caterpillar droppings for use as substrate for fungal gardens. In Corcovado National Park I observed workers regularly visiting extrafloral nectaries of Passiflora pittieri.

Florida
Snelling and Longino (1992) - The following biological information has been provided by J.C. Trager for two samples collected 16 June, 1984 in Gainesville:

These ... were under boards in a weedy lot next to my lab. The brood and fungus gardens of the colonies were kept apart but adjacent on grass stolons or compacted grass blades near the center of single nearly round 5-8 cm-diam. chambers, 1-2 cm deep. Males were clustered on the underside of the board (the warmest, driest part of the nest). The insect fragments, grasshopper feces, etc. collected with one series were heaped separately at opposite sides of the periphery of the nest chamber. This rigid compartmentalization of castes and materials is typical of... this ant. [Queens are usually] associated with the brood [and] most often there are 1 or 2 queens per nest, but I've seen 3 or 4 on occasion. Mating flights take place at the first faint light of dawn, following heavy rains alter a dry spell during the summer months.

Deyrup, Davis & Cover (2000): This species appears to have entered the state from the north or northwest, where it is most common, but it now occurs throughout the state. It is found in a great variety of natural and modified habitats. This is a fungus-growing species that is unlikely to compete with other arthropods, with the exception of Trachymyrmex septentrionalis in sandy uplands and the supposedly native Cyphomyrmex minutus in south Florida. It is possible that some scavenging arthropods will be affected by high populations of C. rimosus, but in general this species will probably have minimal impact on native species.

Nomenclature

 *  rimosus. Cryptocerus rimosus Spinola, 1851b: 49 (w.m.) BRAZIL. [Also described as new by Spinola, 1853: 65.] Emery, 1894c: 224 (q.); Wheeler, G.C. 1949: 668 (l.). Combination in Cyphomyrmex: Emery, 1893h: 2; in Atta (Cyphomyrmex): Forel, 1912e: 188; in Cyphomyrmex: Bruch, 1914: 217. Senior synonym of difformis: Forel, 1893e: 607; Emery, 1894c: 224; of cochunae, fuscus (and its junior synonyms curiapensis, fuscula): Snelling, R.R. & Longino, 1992: 491. See also: Smith, D.R. 1979: 1410.
 * difformis. Meranoplus difformis Smith, F. 1858b: 195 (w.) BRAZIL. Roger, 1863a: 210 (q.m.). Combination in Cataulacus: Roger, 1863a: 210; in Cyphomyrmex: Mayr, 1887: 558. Junior synonym of minutus: Roger, 1863b: 40; of rimosus: Forel, 1893e: 607; Emery, 1894c: 224; Snelling, R.R. & Longino, 1992: 491. [Note. The name was misspelled as deformis by Roger, 1863a: 210 and many subsequent authors.]
 * fuscus. Cyphomyrmex rimosus var. fuscus Emery, 1894c: 225 (w.q.m.) BRAZIL. Senior synonym of curiapensis, fuscula: Weber, 1958d: 260. Junior synonym of rimosus: Snelling, R.R. & Longino, 1992: 491.
 * fuscula. Cyphomyrmex rimosus var. fuscula Emery, 1924d: 342. [Unnecessary replacement name for fuscus Emery, 1894c: 225.] Subspecies of rimosus: Santschi, 1931e: 279; Weber, 1940a: 411 (in key). Junior synonym of fuscus: Weber, 1958d: 260.
 * curiapensis. Cyphomyrmex rimosus subsp. curiapensis Weber, 1938b: 190 (w.q.m.) VENEZUELA. Junior synonym of fuscus: Weber, 1958d: 260.
 * cochunae. Cyphomyrmex rimosus subsp. cochunae Kusnezov, 1949d: 439 (w.) ARGENTINA. Raised to species: Kusnezov, 1957b: 10 (in key). Subspecies of rimosus: Kempf, 1966: 162. Junior synonym of rimosus: Snelling, R.R. & Longino, 1992: 491.

Longino (2004) provides the following concerning the status of this species:

Snelling and Longino (1992) distinguished three similar species, Cyphomyrmex hamulatus, Cyphomyrmex minutus, and rimosus, based on differences in size, pilosity, and extent of the median basal groove of the first gastral tergite. Subsequently I have not been able to differentiate these taxa. There is abundant geographic variation. In some localities it appears that there are discrete sympatric forms, but in other areas the distinction is blurred. For example, in Florida there are two discrete forms, a native species that is relatively small and an introduced species that is larger and darker. The key in Snelling and Longino would separate these into minutus and rimosus, respectively. In Costa Rica, specimens that are collected from open areas, usually by finding nests in the soil or foragers on the surface, are relatively larger and with longer scapes than specimens found in wet forest leaf litter, but the size distributions overlap. Until further evidence for discrete species is produced, I prefer to call them all C. rimosus.

This is a problem for Florida, where there are clearly two species, one native and one introduced. The introduced form is similar to the types of Emery's fuscus, from Brazil (fuscus was synonymized under rimosus by Snelling and Longino). Cyphomyrmex rimosus s.l. may be a polytypic species, in which the native form gradually changes as populations extend through Central and South America, such that the southernmost populations are reproductively isolated from the northernmost populations and remain separate when placed in sympatry through introduction. Alternatively, there could be a complex mosaic of cryptic species, with Florida just being a simplified and more visible example of what occurs throughout the range.

Worker
ha il 2.° segmento del peduncolo poco piu largo che lungo e le sporgenze del torace forti e acute, specialmente Ie punte laterali del pronoto. La forma del peduncolo e descritta esattamente da Smith, ed. e quella sulla quale mi appoggio per stabilire la sinonimia del Meranoplus difformis con la forma descritta da Spinola.

Queen
il metanoto discende molto ripido e in linea quasi retta, se si guarda di profilo, ed e armato di un paio di piccoli denti o tubercoli; il peduncolo e piu largo che nella regina.

Male
il capo e relativamente stretto, con gli angoli posteriori acutissimi; il 2.° segmento del peduncolo meno di una volta e mezzo largo quanto e lungo.