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Cardiocondyla venustula is a small (~ 2 mm), nondescript, uniformly dark brown species with short antennal scapes, propodeal spines reduced to small angles, and without erect hairs on its mesosoma. The species is a successful tramp ant and has spread from its putatively native range in Africa to the southeastern United States, the Caribbean and Hawaii (Seifert, 2003). Despite its success at invading new habitats, C. venustula remains an inconspicuous member of the ant fauna across its range, and is not reported to cause harm to either humans or native species. Cardiocondyla venustula is known to be polydomous and polygynous (Seifert, 2003).
Native range. Africa: Zimbabwe, Mozambique, Namibia (Seifert, 2003).
Introduced range. Carribean. USA: Arkansas, Hawaii, Florida, Louisiana.
The most thorough account of the biology of this tramp ant is Wilson’s (1960)observations from Puerto Rico (the type locality of the species). It was abundant in the lowlands, especially in urban and other cultivated areas near the shore. Nests of one to two hundred workers were found in open soil. Nests were polydomous, with two or three entrances no farther than two meters apart, and these entrances were often ringed with debris. Foraging occurred most intensely during the middle hours of the day, from late morning to middle afternoon. The diet consisted of small pieces of scavenged arthropods and readily accepted sucrose solution. The workers were observed to forage in more direct and efficient paths than were found for C. mauritanica and C. emeryi (Creighton & Snelling, 1974). Wilson also gives a very detailed account of the ‘tandem running’ foraging strategy employed by C. venustula and some of its congeners.
The male caste of C. minutior is dimorphic. Wingless, ergatoid males of the tramp ant Cardiocondyla minutior attack & kill their young ergatoid rivals in an attempt to monopolize mating with female gynes reared within the colony (Frohschammer & Heinze, 2009b). Frohschammer & Heinze (2009b)also reported a novel behavior not previously reported from social insect males in which the ergatoid males spread out in the natal nest and defend territories against other males.
Cardiocondyla venustula occurs in low abundance throughout Florida where it nests in open areas such as fields and beaches (Deyrup et al., 2000). The first published record was from M.R. Smith (1944), though it was collected there in 1932. It has also been recorded from Arkansas (Warren & Rouse, 1969), Louisiana (Dash & Hooper-Bùi, 2008), and Hawaii (Krushelnycky et al., 2005; Reimer, 1994; Wetterer, 1998; Wetterer et al., 1998a).
Among introduced Cardiocondyla species, C. venustula (together with C. kagutsuchi, C. mauritanica and C. minutior) is differentiated from C. emeryi, C. obscurior and C. wroughtonii by (1) its weakly impressed to absent metanotal groove; (2) short propodeal spines that are reduced to right angles (those of C. minutior are of moderate length); and (3) a postpetiole that is lower than the petiole and lacking a distinct ventral bulge. Cardiocondyla venustula is separated from C. kagutsuchi and C. mauritanica by (1) the more rounded sides of the postpetiole in dorsal view, which give the postpetiolar disc a more ovoid (versus hexagonal) appearance; and (2) the longer petiolar peduncle (length which does not taper gradually into the node.
Diagnosis among workers of introduced and commonly intercepted ants in the United States. Worker caste monomorphic. Head shape subrectangular. Antenna 12-segmented. Antennal club 3-segmented. Antennal scapes easily extended beyond eye level but scapes do not extend beyond posterior margin of head. Antennal scrobe lacking. Antennal insertion not surrounded by a raised sharp-edged ridge. Eyes greater than 5 facets; not unusually large (distinctly less than half head length). Posterolateral corners of head unarmed, without spines. Mandibles triangular. Mesosoma lacking erect hairs. Metanotal groove absent to shallow; not distinctly impressed. Pronotal spines absent. Propodeal spines short. Slope of mesosoma gradual. Waist 2-segmented. Petiole with a distinct and upright node; lacking large subpetiolar process. Petiolar peduncle long (length distinctly twice or more than height); does not taper gradually into node. Postpetiole appearing swollen. In dorsal view postpetiole wider than long and much broader than petiole; with gently rounded anterolateral corners; sides rounded, giving the postpetiolar disc a more ovoid than hexagonal appearance. Postpetiole lower than petiole and lacking a distinct ventral bulge. Upper surface of gaster attached to postpetiole. Color uniformly dark brown.
Creighton, W.S. & Snelling, R.R. (1974) Notes on the behavior of three species of Cardiocondyla in the United States (Hymenoptera: Formicidae). J. N. Y. Entomol. Soc., 82, 82-92.
Dash, S.T. & Hooper-Bùi, L.M. (2008) Species diversity of ants (Hymenoptera: Formicidae) in Louisiana. Ann. Entomol. Soc. Am., 101, 1056-1066.
Deyrup, M. (2003) An updated list of Florida ants (Hymenoptera: Formicidae). Florida Entomol., 86, 43-48.
Deyrup, M., Davis, L. & Cover, S. (2000) Exotic ants in Florida. Trans. Am. Entomol. Soc., 126, 293-326.
Frohschammer, S. & Heinze, J. (2009) Male fighting and "territoriality" within colonies of the ant Cardiocondyla venustula. Naturwissenschaften, 96, 159-163.
Krushelnycky, P.D., Loope, L.L. & Reimer, N.J. (2005) The ecology, policy, and management of ants in Hawaii. Proc. Hawaii. Entomol. Soc., 37, 1-22.
Reimer, N.J. (1994) Distribution and impact of alien ants in vulnerable Hawaiian ecosystems. In: Williams, D.F. (Ed.) Exotic ants. Biology, impact, and control of introduced species. Westview Press, Boulder. xvii + 332 p., pp. 11-22.
Seifert, B. (2003) The ant genus Cardiocondyla (Insecta: Hymenoptera: Formicidae) - A taxonomic revision of the C. elegans, C. bulgarica, C. batessi, C. nuda, C. shuckardi, C. stambuloffi, C. wroughtoni, C. emeryi, and C. minutior species groups. Ann. Naturhist. Mus. Wien Ser. B. Bot. Zool., 104, 203-338.
Smith, M.R. (1944) Additional ants recorded from Florida, with descriptions of two new subspecies. Florida Entomol., 27, 14-17.
Warren, L.O. & Rouse, E.P. (1969) The ants of Arkansas. University of Arkansas, Arkansas Agricultural Experiment Station, Bulletin No. 742, 68 p.
Wetterer, J.K. (1998) Nonindigenous ants associated with geothermal and human disturbance in Hawai'i Volcanoes National Park. Pac. Sci., 52, 40-50.
Wetterer, J.K., Banko, P.C., Laniawe, L.P., Slotterback, J.W. & Brenner, G.J. (1998) Nonindigenous ants at high elevations on Mauna Kea, Hawai'i. Pac. Sci., 52, 228-236.
Wheeler, W.M. (1908) The ants of Porto Rico and the Virgin Islands. Bull. Am. Mus. Nat. Hist., 24, 117-158.
Wilson, E.O. (1960) Communication by tandem running and ant genus Cardiocondyla. Psyche, 66, 29-34.
Found most commonly in these habitats: 13 times found in grassland, 7 times found in Urban garden in grassland, 1 times found in clearing in mesophyl forest, 3 times found in Maize field, 1 times found in Lydenburg Thornveld, 1 times found in transitional moist forest, 1 times found in Gold Reef Mountain Bushveld, 1 times found in Heavily grazed grassland, 1 times found in Rehabilitated waste rock dump, 24 degree slope, 1 times found in ridgetop cloud forest, ...
Found most commonly in these microhabitats: 5 times leaf litter, 1 times foragers on cement slab, 1 times on ground, 2 times beating vegetation.
Collected most commonly using these methods: 12 times Pitfall trap, 10 times Hand collected, 5 times Winkler, 2 times search, 2 times Beating, 1 times hand collecting, 1 times Pitfall trap, 5 days, 0 times grassy roadside.
Elevations: collected from 5 - 2000 meters, 1466 meters average