Cardiocondyla emeryi is an accomplished tramp species that originated in Africa and has since spread across the globe’s tropical and subtropical regions (Seifert, 2003a). The species is very small and difficult to distinguish from its trampy congeners, and occurs in both light and dark morphs (Seifert, 2003a). Cardiocondyla emeryi is among the few introduced ant species for which a moderate amount of natural history information is known that is not also a significant pest. It is omnivorous, polygynous, ground-nesting species capable of dispersing by colony budding, and it lives in small colonies (Creighton & Snelling, 1974; Heinze et al., 2006; King & Porter, 2007; Seifert, 2003a). The strategies of Cardiocondyla species as successful tramp species is reviewed by Heinze (2006).
The biology of a free and laboratory colony of Cardiocondyla emeryi introduced in Texas was chronicled in detail by Creighton (Creighton & Snelling, 1974). The observed colony’s nest was a tiny, circular opening about one millimeter in diameter in soil. He reported the species as being omnivorous, equally likely to take nectar as protein, and proposed that the species probably hunts small, soft-bodied insects and scavenges larger ones. Workers of aggressive superior species such as Pheidole dentata, Solenopsis geminata, and Linepithema humile were observed to shrink back when encountering foragers of C. emeryi, which suggested to Creighton the emission of effective repellents. The species was observed forage singly or in tandem pairs, but always with frequent stops and in erratic directions. (In Fiji, however, the species was observed to form relatively strong recruitment trails (Sarnat & Economo, In Press), as evidenced by the large number of workers videotaped at a bait (2008b)). The developmental periods of the captive colony were observed as follows: Egg to larva 12 days, larva to pupa 27 days, pupa to adult 16 days, egg to adult 55 days.
Seifert (2003a)attributed the unusual success of Cardiocondyla species establishing outside their native range by the very small space needed for nest construction, the expressed polygyny in several species, a sufficient survival rate after shortage of water, and in particular the fact that, in some species, a dozen of detached workers with brood can establish a fully reproductive new colony containing all castes.
In the United States, C. emeryi is known from Texas (Creighton & Snelling, 1974), Florida (Deyrup, 1991;2003; Deyrup et al., 2000), and Hawaii (Krushelnycky et al., 2005). In Hawaii the species is reported to occur in low density, polygynous colonies in lowland communities, and is not believed to have a large impact on the native invertebrate community (Reimer, 1994).
Not generally considered a significant pest species.
Diagnosis of worker among Antkey species. 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 6 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 distinctly impressed. Pronotal spines absent. Propodeal spines relatively long. Slope of mesosoma gradual. Waist 2-segmented. Petiole with a distinct and upright node; lacking large subpetiolar process. Petiole with peduncle. Postpetiole appearing swollen, in dorsal view wider than long and much broader than petiole; attached to lower surface of gaster. Postpetiole as high as petiole and with a distinct ventral bulge, postpetiole in dorsal view with gently rounded anterolateral corners. Color of gaster often darker than the rest of body.
The genus was revised on a global scale by Seifert (2003a), who noted that the cosmopolitan population of C. emeryi shows extreme polymorphism in microsculpture clearly exceeding the usual intraspecific variability known for Cardiocondyla, and that two color forms can be distinguished as follows. Light form: lateral area of mesosoma, waist, and appendages yellowish; scutellum, gaster, and antennal club dark brown; remaining body parts yellowish brown. Dark form: whole body dark brown; coxae, femora, tibiae, scape, base of funiculus, and ventrolateral area of pronotum yellowish.
Among introduced Cardiocondyla species, C. emeryi (together with C. obscurior and C. wroughtonii) is differentiated by (1) a distinctly impressed metanotal groove, (2) relatively long propodeal spines, and (3) a postpetiole that is as high as the petiole and possessing a distinct ventral bulge. It is distinguished from C. obscurior and C. wroughtonii by the postpetiole, which in dorsal view has gently rounded (versus sharply angled in C. obscurior and C. wroughtonii) anterolateral corners.
Cardiocondyla obscurior, Cardiocondyla wroughtonii.
Native range: Africa
Current range includes. Mauritius, Madeira, Canary Islands, Cape Verde Islands, St. Helena, Morocco, Israel, Egypt, Sudan, Yemen, Nigeria, Angola, Botswana, Burundi, Rwanda, Uganda, Tanzania, Cameroon, South Africa, Madagascar, Seychelles, Chagos Island, Sri Lanka, Nepal, Hawaii, entire Caribbean, Florida, Brazil, Fiji, Samoa, Costa Rica.
Intercept records: New Zealand (Ward, 2007); USA (USNM specimens).