Ponera clavicornis

This is an exceptionally adaptable and widespread species. It has been collected from primary lowland rainforest (Espiritu Santo), second-growth lowland rainforest (Bubia), foothills forest (Bisianumu), and true mid-mountain forest (Tumnang), under a variety of local ecological conditions (Wilson, 1957). Wilson (1957) reports a small colony nesting under the bark of a large "passalid-stage" log on the ground; larvae at various sages of development and cocoons were present. In Australia it occurs in rainforest where it has been encountered in leaf litter and under bark.

Identification
Taylor (1967) - Easily recognized by the following combination of characters:

1. Moderately small size (head width 0.43-0.47 mm).

2. Small to medium size eyes, their diameter 0.02-0.05 mm, with 2 to 6 indistinct facets; situated about 0.9 X the distance from lateral occipital border to midpoint of anterior genal border.

3. Distinctive heavy sculpturing, especially the regular dense puncturation of head and mesosomal dorsum.

4. Absence of a distinctly incised mesometanotal suture on mesosomal dorsum (this suture may be represented by a faint impression which does not break the underlying sculpture, but in most specimens it is totally unrepresented).

5. Pilosity very sparse, consisting of a few hairs on mandibles, clypeus, and frontal lobes, the petiolar dorsum, the terminal gastric tergites and all gastric sternites. Erect hairs from cranium and dorsum of mesosoma, and in most samples, from first two gastric tergites.

Ponera augusta has similar sculpturation but it has a wider head, a distinct mesometanotal suture, and normal pilosity. Ponera elegantula has similarly reduced pilosity and lacks the mesometanotal suture; it is, however much less heavily sculptured. Both augusta and elegantula have much larger eyes than clavicornis.

Distribution
This taxon was described from New Guinea. It is known from Solomon Islands, Vanuatu and Australia.

Biology
Taylor (1967) - I encountered Ponera clavicornis in mid montane oak, Araucaria klinkii rain forest near Wau, NE New Guinea. Wilson found it to be ecologically very adaptable and collected it in primary and secondary lowland forest, foothill forest, and true midmountain forest under a variety of conditions. Altitudinal range of the collections is from sea level to 1500 m in New Guinea, as well as from high elevation forest on Guadalcanal.

Nomenclature

 *  clavicornis. Ponera clavicornis Emery, 1900c: 317, pl. 8, figs. 7, 8 (w.) NEW GUINEA. Taylor, 1967a: 74 (q.). Combination in Selenopone: Wheeler, W.M. 1933g: 22; in Ponera (Hypoponera): Santschi, 1938b: 79; in Ponera: Wilson, 1957b: 377; Taylor, 1967a: 73.

Worker
Wilson (1957) - HW 0.43-0.47 mm, HL 0.52-0.59 mm, SL 0.35-0.42 mm, cr 81-85, SI 80-89, PW 0.32-0.37 mm, dorsal petiole width 0.27-0.32 mm. Mandibles with three well developed teeth occupying about the apical half of the masticatory border ; the basal half occupied by an indeterminate number of minute denticles. Eye as described for P. selenophora. Antennal club relatively slender, 5-jointed. Posterolateral margins of propodeum relatively poorly defined, seen from directly above forming an angle of only slightly less than 90°. Posterior face of petiolar node seen from directly above almost perfectly straight. Subpetiolar process variable in shape, ranging from a rudimentary convexity to a strong right-angular projection. Mandibles smooth and shining; clypeus feebly shagreened and shining over most of its surface; entire remainder of the head densely, finely, and evenly punctate (the punctures mostly under 0.01 mm in diameter) and completely opaque. Entire dorsal and lateral alitrunca;l surfaces similarly punctate and opaque, except for the ventral margins of the sides of the pronotum, a limited central longitudinal strip on the sides of the propodeum, and the lower half of the posterior propodeal face, which surfaces are more or less smooth and shining. Dorsal and lateral surfaces of petiolar node somewhat less densely punctate than head and alitrunk, subopaque; anterior and posterior faces more or less smooth and shining. First several gastric tergites also somewhat less densely punctate, subopaque to feebly shining.

Pilosity completely lacking on head and alitrunk except for a few erect hairs on the mandibles, clypeus, and frontal lobe area. Petiolar node and first two gastric tergites bare to sparsely pilose; terminal gastric tergites and all gastric sternites abundantly pilose.

Body (except mandibles and apical gastric segments) piceous brown, approaching jet black. Mandibles, apical gastric segments, and appendages yellowish brown.

Geographic variation. The series from Espiritu Santo, New Hebrides, have somewhat longer scapes than those from New Guinea (Sr 86-89 as opposed to 80-84).

The series from Bisianumu, Papua, ha.ve the first two gastric tergites pilose; in side view 5-10 standing hairs are visible along the profile of the first tergite. The series from Tumnang, N-E. New Guinea, and from the New Hebrides have the first two gastric tergites bare of pilosity. The series from Bubia, N-E. New Guinea, a geographically intermediate locality, has the tergites intermediately pilose: 1-3 standing hairs are visible along the profile of the first tergite.

Taylor (1967) - Workers of Ponera clavicornis should be easily recognized using the keys, figures and diagnostic details presented here. The following qualifications and additions to Wilson's diagnosis should be noted:

1. Known ranges for dimensions and indices (with exception of 1 small individual discussed below) are: HL 0.52-0.59 mm; HW 0.43-0.47 mm; SL 0.35-0.42 mm; CI 81-85; SI 80-89; PW 0.32-0.37 mm; PNL 0.20-0.22 mm; PH 0.28-0.35 mm; DPW 0.27-0.32 mm; PNI 80-89.

2. Palpal formula: Maxillary 2: Labial 2 (several specimens inspected).

3. Distinct medium clypeal tooth not developed, but a shallow obtuse tumosity may be present in the middle of anterior clypeal border.

4. Scapes failing to reach medium occipital border by a distance of about 1/4 to 1/3 their maximum thickness.

5. The funicular club was said by Wilson to be 5-segmented. Actually the degree of development of the club is quite variable; it may appear to be completely undifferentiated, or rather indistinctly 4- or 5-segmented, even in specimens from a single sample.

6. Lateral mesonotal suture completely absent in most specimens, but a slight, superficial trace of it is present in others. This never completely breaks the sculpturation.

Queen
Taylor (1967) - Based on 2 alates and a dealate, collected in association with workers at Bisianumu, near Sogeri, SE New Guinea by E. O. Wilson, and 2 dealate queens from Tumnang and the lower Busu River, NE New Guinea (E. O. Wilson). The last specimen was not associated with workers, but seems to be satisfactorily placed under clavicornis.

The Bisianumu queens have the following dimensions and indices: HL 0.55-0.57 mm; HW 0.47-0.49 mm; SL 0.38-0.40 mm; CI 85-86; SI 81-83; PW 0.44-0.46 mm; PNL 0.17-0.18 mm; PH 0.36-0.39 mm; DPW 0.31-0.33 mm; PNI 70-72; maximum diameter of compound eye 0.15-0.16 mm; ocular index 31-34; palpal formula: Maxillary 2: Labial 2 (1 specimen inspected). Differing from workers in usual characters of full sexuality, resembling them in color, development of sculpturation, pubescence and pilosity. Wing venation of "coarctata type."

Additional References
Emery, C. (1900). Formicidarum species novae vel minus cognitae in collectione Musaei Nationalis Hungarici quas in Nova-Guinea, colonia germanica, collegit L. Biró. Publicatio secunda. Természetrajzi Füzetek, 23: 310–338.