Cardiocondyla compressa

This species is only known from a single site on Hammond Island (-10.55, 142.20) in the Torres Strait, Queensland, Australia.

Identification
A member of the Cardiocondyla nuda group.

This species is characterized by a very narrow petiole, small size and reduced sculpture.

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
 * Discriminant 538.753×PLG - 72.321×CL + 174.434×MpGr + 46.778×SL + 4.27 < 0
 * Petiole very narrow, discriminant 124.351×PEW - 1.129×CW - 13.561 < 0

where:


 * CL: Maximum cephalic length in median line; the head must be carefully tilted to the position yielding the true maximum; excavations of hind vertex and/or clypeus reduce CL.


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


 * MpGr: Depth of metanotal groove or depression, measured from the tangent connecting the dorsalmost points of promesonotum and propodeum.


 * PEW: Maximum width of petiole.


 * 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 based on Regional Taxon Lists
Australasian Region: Australia.

Nomenclature

 *  compressa. Cardiocondyla compressa Seifert, in Seifert et al., 2017: 351, figs. 17-19 (w.) AUSTRALIA.

Worker
Small body size, CS 410 μm. Head elongated, CL/ CW 1.200. Postocular distance large, PoOc/CL 0.476. Eyes small, EYE 0.225. Frontal carinae immediately caudal of the FRS level parallel or slightly converging. Sculpture on head, mesosoma and waist much weaker than usually seen in the Cardiocondyla nuda group; foveolae on vertex less deeply impressed, of 14–19 μm diameter, and with an inner corona (a flat tubercle) of 7–9 μm diameter having the base of a decumbent pubescence hair in its center. Longitudinal sculpture on vertex almost absent, 1–2 weak longitudinal carinulae run parallel to frontal carinae in short distance to these. Weak semicircular rugae are found around the antennal fossae. Lateral mesosoma on whole surface regularly microreticulate-foveolate; longitudinal sculpture except for 4–6 weak and short carinulae on metapleuron completely absent; dorsal mesosoma rather shining and with shallow reticulate-foveolate-shagrinate microsculpture. Sides of petiole with a weakly sculptured microreticulum, dorsal petiole and postpetiole with shining, with only a delicate microreticulum. Cuticular surface of first gaster tergite rather smooth and shining but on its whole surface with a well-developed microreticulum. Pubescence hairs on gaster tergites moderately long, PLG/CS only 5.88%. Metanotal depression very shallow, MGr/CS 1.1%. Propodeal spines short but clearly longer than in the Cardiocondyla mauritanica species complex. Dorsal propodeum sloping down to base of spines under an angle of 20°. Petiole very narrow, PEW/CS 0.250; petiole node much longer than wide. Postpetiole in dorsal view with convex (not angulate) sides and rather low, PPH/CS 0.327; postpetiolar sternite not bulging, thus approaching the condition in the C. mauritanica complex. Head, mesosoma, waist and appendages yellowish, gaster significantly darker. Morphometric data of 2 workers given in Table 2.

Type Material
The holotype worker and one paratype worker without gaster are on the same pin labelled "TORRES STRAIT Hammond I. 10.33Sx142.12E", "4–8 July 1974 H. Heatwole et E. Cameron" and "Holotype (top specimen) & Paratype Cardiocondyla compressa Seifert". The types are deposited at.



Etymology
The species epithet refers to the extremely narrow petiole.