Hypoponera natalensis

Identification
See the nomenclature section below.

Distribution
This taxon was described from South Africa.

Nomenclature

 *  natalensis. Ponera coarctata st. natalensis Santschi, 1914e: 7 (w.) SOUTH AFRICA. Combination in P. (Hypoponera): Santschi, 1938b: 79; in Hypoponera: Taylor, 1967a: 12. Raised to species: Santschi, 1938b: 79; Taylor, 1967a: 12. See also: Bolton & Fisher, 2011: 74.

Bolton and Fisher (2011) - H. natalensis and Hypoponera austra share the character of having a transverse impression across the base of the posterior face of the petiole node, above the peduncle. The impression is not deep and may be difficult to discern in direct posterior view, but in posterodorsal view its upper margin appears as a dark line, located well above the peduncle. In natalensis the impression terminates at either side in a short oblique cuticular ridge that is usually clearly visible in profile, but this may be missing in austra. A similar transverse impression can be seen in Hypoponera exigua and Hypoponera traegaordhi, but in these the impression is spanned by a series of short cuticular ridges that radiate upward from the posterior peduncle. The radiating ridges of exigua and traegaordhi are convergent on the species related to Hypoponera jeanneli and Hypoponera hebes, but in these the ridges are directly on the flat posterior surface and are not confined within an impression that has a sharply delineated upper margin.

H. natalensis and austra are best separated by the condition of the petiole, which in natalensis is shorter and higher in profile (LPeI 41–47) and distinctly broader in relation to its length in dorsal view (DPeI 160–187), than in austra (LPeI 47–56, DPeI 137–150). In more relative features, the metanotal groove often retains a vestigial presence in natalensis but is always absent in austra, and the cross-ribs of the cinctus of the second gastral tergite are distinctly coarser and more strongly developed in natalensis than in austra.

A third species in this complex is Hypoponera meridia, which although lacking the transverse impression on the posterior surface of the petiole, often exhibits a slender transverse ridge immediately above and adjacent to the posterior peduncle. This is a smaller species, HW 0.38–0.42, SL 0.32–0.36, PeH 0.28–0.32, as compared to the combined measurements of HW 0.46–0.57, SL 0.38–0.50, PeH 0.34–0.44 in natalensis and austra.

In South Africa there appears to be a size-related morphoclinal reduction in several characters that spans the following species, listed in decreasing order of size: spei (and boerorum) – natalensis – austra – meridia – perparva. Along the cline there is a gradual reduction to loss of eyes, reduction to loss of metanotal groove, reduction in height of petiole and decrease in density and intensity of development of cross-ribs in the cinctus of the second tergite. If this perceived morphocline is real, then obviously the placement of spei and boerorum in a group separate from the others is artificial.

Worker
Bolton and Fisher (2011) - Measurements: HL 0.62–0.69, HW 0.48–0.57, HS 0.555–0.630, SL 0.42–0.50, PrW 0.38–0.42, WL 0.82–0.92, HFL 0.40–0.50, PeNL 0.16–0.18, PeH 0.36–0.44, PeNW 0.26–0.32, PeS 0.260–0.313 (12 measured). Indices: CI 76–83, SI 84–90, PeNI 68–76, LPeI 41–47, DPeI 160–187.

Eyes vestigial to absent, usually represented by a small, depigmented spot that appears to be the remnant of a single ommatidium; sometimes no trace of an eye spot. In full-face view apex of scape, when laid straight back from its insertion, just fails to reach, or just touches, the midpoint of the posterior margin; SL/HL 0.67–0.73. Reticulate-punctulate sculpture of cephalic dorsum fine, but head more densely sculptured than pronotal dorsum. Lateroventral surfaces of head with extremely feeble punctate sculpture, merely of separated small superficial punctures on an otherwise smooth surface. With mesosoma in dorsal view the metanotal groove is usually, but not always, vestigially represented by a faint transverse line that indicates the junction of the mesonotum and propodeum, but never with a strong impression that interrupts the surface; sometimes without trace of the metanotal groove. Propodeal declivity separated from sides by blunt marginations. Mesopleuron smooth and shining. Petiole in profile with the node relatively short and high, the anterior and posterior faces parallel, not convergent dorsally; dorsal surface broadly convex. Subpetiolar process with a low, blunt, ventral angle that is usually obtuse. Posterior surface of petiole node with a shallow transverse groove or impression above the peduncle, the upper margin of the impression appears as a transverse dark line or ridge in posterodorsal view. Each end of the impression usually terminates in a short oblique ridge that is visible in profile, but there are no cuticular ridges radiating upwards into the impression from the posterior peduncle. Maximum width of first gastral tergite in dorsal view slightly less than the width of the second tergite at its midlength. Base of cinctus of second gastral tergite with strong, dense cross-ribs. Posttergite of second gastral segment, from posterior margin of cinctus to apex, distinctly broader than long. Disc of second gastral tergite shallowly reticulate-punctate to microreticulate. With first gastral segment in profile the dorsum with sparse short standing setae. Full adult colour yellowish brown to light brown.

Type Material
Syntype workers, SOUTH AFRICA: Natal, Richmond, 25.iii.05 (I. Trågärdh) [examined].