Cardiocondyla nuda

Once thought to be a cosmopolitan tramp species, revisionary work has shown the range of this species is restricted from Papua New Guinea and Australia east to Samoa. Three of six colonies excavated in 2014 in Cairns contained multiple fertile queens. Males are ergatoid, kill callow males and fight with adult males. Slightly larger, ergatoid males with stubby wings may occasionally occur (observations in the laboratory of J. Heinze) (Seifert et al., 2017).

Identification
A member of the Cardiocondyla nuda group.

Seifert et al. (2017) - There is no doubt that species separation in the C. nuda group is difficult. It requires careful consideration of character definitions and the use high-resolution optical and measurement systems. The diagnose presented here uses numerous morphological characters to achieve an acceptable identification error rate.

Meeting the following definition:


 * Discriminant 176.328×PPH - 49.049×CW + 51.521×SP - 59.844×PPW + 6.61 > 0
 * Discriminant 60.625×SL - 80.384×SP - 61.223×PPW + 356.511×PLG - 12.585 > 0

where:


 * CW: Maximum cephalic width; the maximum is found usually across and including the eyes, exceptionally posterior of the eyes.


 * PLG: Mean length of pubescence hairs on dorsum of first gaster tergite as arithmetic mean of at least 7 measurements measured at magnifications of 320x.


 * PPH: Maximum postpetiole height; the lateral suture of dorsal and ventral sclerites is the reference line perpendicular to which the maximum height of postpetiole is measured.


 * PPW: Maximum width of postpetiole.


 * SL: Maximum straight line length of scape excluding the articular condyle given as the arithmetic mean of both scapes.


 * SP: Maximum length of propodeal spines; measured in dorsofrontal view along the long axis of the spine, from spine tip to a line that orthogonal to the long axis and touches the bottom of the interspinal meniscus (Fig. 3). Left and right SP are averaged. This mode of measuring is less ambiguous than other methods but yields higher spine length values in species with reduced spines. This is the case in the dentiform spines found in the C. nuda group where it is difficult to correctly define the long axis. In such cases, the deviation of the assumed spine axes from longitudinal mesosomal axis should not exceed 30°.

Distribution
The distributional range of C. nuda extends over 6000 km in an east-west direction and includes the coast line of North and East Australia, Papua New Guinea and probably all Polynesian islands east to Samoa. The presence of populations in very isolated Polynesian islands (Fiji and Samoa) as early as the mid 19th century suggests that there was some natural way of dispersal over a huge Pacific area before modern ship traffic and goods transport developed. (Seifert et al., 2017)

Distribution based on Regional Taxon Lists
Australasian Region: Australia. Indo-Australian Region: Fiji, Micronesia (Federated States of), New Guinea, Samoa, Solomon Islands, Tonga, Vanuatu, Wallis and Futuna Islands.

Biology
In Australia this species is found in a range of habitats from natural to urban, and from coastal dunes and grasslands to rainforest. It prefers areas with annual rainfall > 1000 mm.

Nomenclature

 *  nuda. Leptothorax nudus Mayr, 1866a: 508 (w.) FIJI IS. Emery, 1897c: 588 (q. ergatoid m.); Wheeler, G.C. & Wheeler, J. 1973a: 27 (l.); Imai, et al. 1984: 6 (k.). Combination in Cardiocondyla: Forel, 1881: 6. Current subspecies: nominal plus sculptinodis. See also: Seifert, 2003a: 245.

Taxonomic Notes
Seifert (2003) - In agreement with the type localities given in Mayr's description the type specimen from Ovalau / Fijis was designated as lectotype. Because of misidentifications, C. nuda has been erroneously termed in the past as cosmopolitan tramp species. Instead, it seems to be restricted to the tropical and subtropical Pacific region. Investigation of authentic material showed that Palaearctic "C. nuda" (sensu PISARSKI 1967, BOLTON 1982, HEINZE & al.1993) turned out to be Cardiocondyla mauritanica while Japanese-Pacific "C. nuda" (TERAYAMA & al. 1992, TERAYAMA 1999) were Cardiocondyla kagutsuchi. Cosmopolitan C. mauritanica and Indomalayan-West Pacific C. kagutsuchi differ from Australasian-Polynesian C. nuda in particular by the wider head, the smaller postocular index, the shorter spines, the lower waist segments, and the larger ratio PEH/PPH. Furthermore, the microreticulum on lateral mesosoma and petiole is less deeply sculptured than in C. nuda, in which it is relatively coarse, giving a perfectly dull surface impression at magnifications < 60x.

Subsequently, Seifert (2008) published revisionary work that separated C. nuda from C. atalanta.

Worker
Seifert (2003) - Small size, CS 468. Head elongated, CL/CW 1.224. Postocular head parallel-sided and very long, PoOc/CL 0.469. Scape of medium length, SL/CW 0.802. Occipital margin straight or slightly concave. Frontal laminae converging immediately caudal of FRS level, FL/FR in lectotype 1.095. Eyes relatively small, EYE 0.233. Foveolae on vertex in dense honey-comb arrangement, deeply impressed, with 17 - 20 µm diameter, and usually with inner corona. Frontal laminae and clypeus with few longitudinal rugulae. Whole mesosoma and lateral petiole with strong microreticulum having mesh diameters of 5 - 13 µm (smallest on petiole sides). Metanotal groove more or less shallow. Spines longer and more erect than in Cardiocondyla mauritanica and rather acute. Postpetiole in dorsal view usually with angulate-convex sides and roughly hexagonal; sides sometimes simply convex, without angular component; bulging postpetiolar sternite resulting in large PPH that is frequently larger than PEH, PEH/PPH 1.009 ± 0.026 [0.964, 1.060]. Surface of first gaster tergite shining and with very delicate microreticulum. Whole head and mesosoma of type specimen concolorous dark brown, gaster blackish brown. Lighter specimens with yellowish brown mesosomas and medium brown heads frequently occur throughout the Pacific region. For morphometric data of 34 workers see Tab. 9.

Queen
Seifert (2003) - Rather small, CS 521. Head much elongated, CL/CW 1.203. Postocular head parallel-sided and very long, PoOc/CL 0.458. Occipital margin straight or slightly concave. Foveolae on vertex in dense honey-comb arrangement, deeply impressed, with 19 -20 µm diameter, and with inner corona. Frontal laminae, clypeus, and small median stripe on vertex longitudinally carinulate-rugulose. Whole mesosoma and lateral petiole with very strong reticulum (or foveolate without interspaces). Spines short but acute. Postpetiole relatively narrow, dorsal aspect with concave anterior margin and angulate-convex sides, only slightly lower than petiole, PEH/PPH 1.061 ± 0.022 [1.028, 1.096]. Whole body concolorous dark brown. For morphometric data of 10 gynes see Tab. 17.

Male
Emery, (1897c) described the ergatoid male.