Attini, Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
rimosus s.l., including minutus and hamulatus (see comments): Southern United States south to Argentina, throughout Caribbean. Costa Rica: widespread in all lowland to mid-elevation habitats.
Mandibles with 5 teeth; preocular carina curving mesad toward frontal carina; antennal scrobe poorly defined; lateral vertex margins forming blunt angles, not produced as acute teeth; pronotum with pair of median tubercles.
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 C. 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.
Snelling and Longino (1992) distinguished three similar species, hamulatus, 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.
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.
John T. Longino, The Evergreen State College, Olympia WA 98505 USA.email@example.com
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