Cardiocondyla thoracica

P.S. Ward found a nest in a rotten log in a New Guinean rainforest. Heinze et al. (2016) described the biology of the population from northern Queensland as follows. Nests are composed of small chambers and were found 1–3 cm deep in red, sandy soil on sun exposed, sparsely vegetated patches between the forest and a roadside ditch. Another colony was found nesting in a cavity of a fallen tree in a streambed. Ten colonies collected in the field contained between seven and approximately 80 workers (median 40) and one to four mated queens which did not show mutual aggression. In three nests a single wingless male was present. Males are exclusively ergatoid and have sickle-shaped mandibles. They appear to widely ignore adult competitors, but grab defenseless, young rivals during or immediately after emergence and besmear them with hindgut secretion. This fluid elicits deadly worker aggression against the besmeared individual.

Identification
Seifert (2022) - Worker: Rather small, CS 479 µm. Head short, CL/CW 1.098. Posterior margin of vertex slightly convex. Postocular head sides convex and less converging than in Cardiocondyla paradoxa, postocular distance moderate (PoOc 0.452). Anterior clypeal margin deeply and broadly excavated, whole area of median clypeus deeply concave. Scape rather long, SL/CS 0.876. Eye rather large, EYE 0.240. Frons wide (FRS/CS 0.286), frontal carinae posterior of the FRS level almost parallel or slightly diverging caudad; planes of frontal laminae sloping mediad by 40°, frontal carinae thus much elevating above the level of posterior clypeus. Mesosoma much less slender than in Cardiocondyla paradoxa, in dorsal view with very prominent pronotal corners each forming an sharp angle of 70°, their distance as wide as posterior head, dorsal mesosoma continuously and roughly linearly narrowing from the wide pronotal corners caudad to spine base. Dorsal mesosomal profile with exception of the angle produced by the corners evenly convex; metanotal depression fully absent or only suggested (MGr/CS 0.63%). Spines sharp and long (SP/CS 0.335), with rather wide basal distance (SPBA/CS 0.333), and straight or very feebly downcurved; their axis in lateral view usually deviating less than 20° from the longitudinal mesosomal axis. Petiolein lateral view high (PeH/CS 0.349), with a short peduncle, a concave anterior and convex dorsocaudal profile. Petiole node in dorsal view longer than wide and narrowing frontad but whole petiole rather wide (PeW/CS 0.286). Postpetiole low (PpH/CS 0.270), in dorsal view wide (PpW/CS 0.525) and with a strongly concave anterior margin. Postpetiolar sternite flat, its anterolateral portions each with a short, upcurved, and shallow carina. Head in overall appearance smooth and very shiny, median and paramedian vertex with small unstructured foveolae of 6–7 µm diameter and 17–21 µm nearest-neighbor distance, on more lateral areas of vertex, in particular the surface frontomedial of the eye, the foveolae are larger and with a structured bottom: 13–19 µm diameter and a central accessory foveola of 5–6 µm diameter (Figure 22D); foveolar interspaces very shiny but with very delicate microreticular structures. Posterior and anteromedian clypeus smooth, in its anterolateral parts rugulose. Frontal laminae in lateral parts rugulose and with well-defined foveolae of 7–13 µm diameter. Dorsal mesosoma, smooth with scattered foveolae of 5–7 µm diameter, lateral mesosoma and waist microreticulate but shiny. 1st gaster tergite in overall impression shiny but with a well-developed microreticulum and a rather short, dilute pubescence (PLG/CS 4.21%, sqPDG 6.54). Whole head capsule and gaster blackish brown. Appendages, mesosoma and waist yellow.

Cardiocondyla thoracica appears rather monomorphous along those 2000 km of its multi-island range and appears unmistakable. It is considered to be of Indonesian origin (Andersen, 2000) and to have spread south during the last ice age when Northern Australia was connected to Papua New Guinea.

Distribution based on Regional Taxon Lists
Australasian Region: Australia. Indo-Australian Region: Indonesia, New Guinea.

Nomenclature

 * . Myrmica thoracica Smith, F. 1859a: 148 (w.) INDONESIA (Aru Is).
 * Type-material: 3 syntype workers.
 * Type-locality: Indonesia: Aru Is (A.R. Wallace).
 * Type-depository: OXUM.
 * Combination in Cardiocondyla: Donisthorpe, 1932c: 455.
 * Status as species: Mayr, 1863: 435; Smith, F. 1871a: 325; Dalla Torre, 1893: 118; Donisthorpe, 1932c: 455; Chapman & Capco, 1951: 130; Bolton, 1995b: 133.
 * Distribution: Indonesia (Aru Is)

Type Material


Myrmica thoracica

Three worker syntypes in. Labelled “Aru.” (= Aru I., New Guinea).

References based on Global Ant Biodiversity Informatics

 * CSIRO Collection
 * Janda M., G. D. Alpert, M. L. Borowiec, E. P. Economo, P. Klimes, E. Sarnat, and S. O. Shattuck. 2011. Cheklist of ants described and recorded from New Guinea and associated islands. Available on http://www.newguineants.org/. Accessed on 24th Feb. 2011.
 * Lucky A., L. E. Alonso, E. Sarnat, and J. Hulr. 2015. Ants and scolytine beetles. In: Richards, S.J. and N. Whitmore (editors) 2015. A rapid biodiversity assessment of Papua New Guinea's Hindenburg Wall region. Wildlife Conservation Society Papua New Guinea Program. Goroka, PNG.
 * Snelling R. R. 1998. Insect Part 1: The social Hymenoptera. In Mack A. L. (Ed.) A Biological Assessment of the Lakekamu Basin, Papua New Guinea, RAP 9. 189 ppages
 * Wilson E. O. 1959. Some ecological characteristics of ants in New Guinea rain forests. Ecology 40: 437-447.