Cardiocondyla minutior

A tramp species that has spread into numerous tropical areas. It is not know to be a pest in any area nor has it been known to cause harm to any native species in its introduced range.

Identification
C. minutior workers can be separated from C. emeryi by its lower profile postpetiole, a lack of an anteroventral bulge on the postpetiole, a lack or near lack of a metanotal groove, longer tergite pubescence, and more developed microsetae on eyes.

Seifert (2003) includes more details about specific morphological measures that separate these species. There is also a key to the holarctic species of Cardiocondyla that includes this and other tropical tramp species.

Sarnat (2008) provides video of foraging workers.

Distribution based on Regional Taxon Lists
Australasian Region: New Zealand. Indo-Australian Region: Guam, Hawaii, Indonesia, Marshall Islands, Micronesia (Federated States of), New Guinea, Northern Mariana Islands. Nearctic Region: United States. Neotropical Region: Barbados, Costa Rica, Dominican Republic, Ecuador, Greater Antilles, Guatemala, Honduras, Mexico. Oriental Region: India, Nepal, Sri Lanka, Vietnam. Palaearctic Region: Japan.

Biology
Seifert (2003): K. Yamauchi (pers. comm 2001) reported for Okinawa the nesting in shallow soil in open, disturbed areas with bare or weakly herbaceous ground. The Japanese population of C. minutior is reported to have a karyotype of 2n = 30 and to produce alate and ergatoid males. The latter perform lethal fighting for exclusive mating (Terayama 1999).

Male-male competition has been studied in this species. An abstract from one of these studies (Heinze et al. 2004): Wingless (ergatoid) males of the tramp ant Cardiocondyla minutior attack and kill their young ergatoid rivals and thus attempt to monopolize mating with female sexuals reared in the colony. Because of the different strength of local mate competition in colonies with one or several reproductive queens, we expected the production of new ergatoid males to vary with queen number. Sex ratios were mostly female-biased, but in contrast to the sympatric species C. obscurior (Cremer and Heinze, 2002) neither the percentage of ergatoid males nor of female sexuals among the first 20 sexuals produced varied considerably with queen number. As in C. obscurior, experimental colony fragmentation led to the production of winged males, whereas in unfragmented control colonies only ergatoid males eclosed.

Nomenclature

 *  minutior. Cardiocondyla nuda var. minutior Forel, 1899a: 120 (w.) HAWAII. Wheeler, W.M. 1922f: 317 (q.); Heinze, 1999: 251 (polymorphic m.). Subspecies of nuda: Smith, M.R. 1944a: 38. Creighton, 1950a: 198. Junior synonym of nuda: Wilson & Taylor, 1967: 55. Revived from synonymy: Heinze, 1999: 251. Senior synonym of tsukuyomi: Seifert, 2003a: 283.
 * tsukuyomi. Cardiocondyla tsukuyomi Terayama, 1999d: 101, figs. 11-13 (w.q.m. ergatoid m.) JAPAN. Junior synonym of minutior: Seifert, 2003a: 283.

Seifert (2003): Intraspecific variability in C. minutior is rather low within the huge range of its distribution, extending over the Neotropic, Polynesian, Australasian, Indo-Australasian, and Oriental regions. Samples from central Sri Lanka have significantly smaller eyes, those from Okinawa, N India, and Nepal shorter heads but all these deviating populations are in the vast majority of other characters consistent with the overall average.

Cardiocondyla tsukuyomi is in body shape and any structural and morphometric character consistent with the worldwide population of C. minutior as it is with the types of C. minutior from Hawaii. The 3 studied type workers of C. tsukuyomi and 4 topotypical non-type workers from Okinawa do not differ from the C. minutior population from outside Okinawa (Tab. 5). Recent mDNA studies have shown that tsukuyomi and minutior cluster closely together, while Cardiocondyla tjibodana and C. minutior could represent separate evolutionary lines (Trindl & Heinze, pers. comm. October 2002).

Worker
Seifert (2003) - Small size, CS 418. Head elongated, CL/CW 1.259. Postocular distance very large, PoOC/CL 0.475. Scape short, SL/CS 0.756. Eye rather small, EYE 0.233, with notable microsetae, the longest measuring 6 - 10 µm. Occipital margin straight or very weakly concave. Frontal carinae slightly converging immediately caudal of FRS level. Anterior clypeal margin with suggested median concavity. Clypeus, frontal laminae, frontal triangle, and very narrow anteromedian stripe of vertex longitudinally carinulate (in some specimens from N India and Nepal such carinulae cover the whole median and paramedian vertex, with reduction of foveolae in these areas). Except for longitudinal rugae on preocular surface, semicircular rugae around antennal fossae, and few short, longitudinal rugae on metapleuron; whole body without any rugosity. Sculpture on paramedian vertex similar to situation in the C. emeryi types, showing deeply impressed, flat-bottomed foveolae of 13 - 18 µm diameter in dense honey-comb arrangement (if not displaced by longitudinal carinulae). Foveolae with an inner corona (margin of a f1at tubercle) of 7 - 8 µm diameter. Mesosoma on whole surface sculptured, rather mat: dorsal mesosoma densely and strongly reticulate-foveolate; lateral mesosoma densely and strongly reticulate; metapleuron with 1 - 4 longitudinal rugae. Waist segments with fully developed, but shallower and finer reticulum than on mesosoma, nodes sometimes slightly shining. First gaster tergite often with very fine microreticulum. Pubescence on whole body long and dense, sqrtPDG 3.34. Dorsal profile of mesosoma rather straight or weakly convex, metanotal groove only suggested or entirely absent. Spines short and acute, their axis in profile deviating by 40 - 45° from longitudinal axis of mesosoma. Petiole in profile with concave anterior face and rounded node that is in dorsal view circular and as long as wide. Postpetiole very low, its sternite completely fiat, without any anteroventral bulge; in dorsal view with angulate-convex sides and straight anterior margin. Colour of head, mesosoma, and waist varying considerably from dirty yellowish to dark dirty brown, gaster dark to blackish brown. For morphometric data of 72 workers see Tab. 14.

Queen
Seifert (2003) - Very small size. Head elongated, CL/CW 1.228. Scape rather short, SL/CS 0.755. Postocular index very large, PoOc/CL 0.459. Eyes with numerous hairs, the longest of them 8 - 11 µm long. Occipital margin more or less straight. Anteromedian clypeal margin straight to slightly convex. Vertex with deeply impressed, flat-bottomed, densely-packed foveolae of 15 - 18 µm diameter which show an inner corona of 7 -9 µm diameter. Paramedian and median areas of vertex with suggested longitudinal rugae. Frontal laminae and clypeus with few longitudinal carinulae. Whole dorsal area of mesosoma with deep, densely-packed foveolae, fragments of longitudinal rugae visible on mesonotum. Lateral lobes of praescutellum connected by a very thin junction or entirely separated. Lateral area of mesosoma foveolate-reticulate, region of metapleural gland bulla with longitudinal rugae. Propodeal spines well-developed, their axis deviating from mesosomal axis in lateral view by 25 -30°. Petiole node foveolate-reticulate, in dorsal view circular. Postpetiole in dorsal view strongly foveolate-reticulate, distinctly wider than long, with straight anterior margin and strongly convex sides. Postpetiolar sternite very flat, without any bulge. Whole body covered by long and dense pubescence. Dorsum of gaster shining, with fine microreticulum. For morphometric data of 14 gynes see Tab. 19.

Type Material
Seifert (2003):

Cardiocondyla minutior: two syntype workers labelled "C. nuda Mayr v. minutior type Forel, Hawai" and "Molockai Mts., 3000 ft. Perkins 1893", MHN Genève.

Cardiocondyla tsukuyomi: 6 paratype workers from the same sample as holotype, labelled: "VI 1988 K.Yamauchi leg., Ada, Okinawa-jima Okinawa Pref." and "Cardiocondyla tsukuyomi Terayama, 1999, Paratype", SMN Garlitz.

Cardiocondyla nuda var. minutior Forel, 1899; Hawaii: Honolulu and Molockai [types investigated].

Cardiocondyla tsukuyomi Terayama, 1999; Ada / Okinawa Island [types investigated], syn.n