Ponera tenuis

Ponera tenuis is found in leaf litter, logs, moss and other situations on the ground, always in rainforests.

Identification
Taylor (1967) - Easily recognized by the combination of medium size (HW 0.40-0.45 mm) with the characters of its species group (4-segmented antennal club and lack of an incised mesometanotal suture). The other 3 tenuis group species, with which tenuis is probably sympatric on New Guinea, are all smaller (HW 0.30-0.34 mm). In Samoa the species group characters are diagnostic. The absence of pupal cocoons provides a useful character for field recognition; this is the only known Ponera with naked pupae.

Distribution based on Regional Taxon Lists
Australasian Region: Australia. Indo-Australian Region: Marshall Islands, Micronesia (Federated States of), New Guinea, Niue, Northern Mariana Islands, Samoa, Solomon Islands, Tonga. Palaearctic Region: China.

Biology
Beyond its habitat affinities, little is known about the biology of Ponera tenuis.

Nomenclature

 *  tenuis. Cryptopone tenuis Emery, 1900c: 321, pl. 8, figs. 21, 22 (w.q.) NEW GUINEA. Combination in Pseudocryptopone: Wheeler, W.M. 1933g: 13; in Ponera: Wilson, 1957b: 373. Senior synonym of huonica: Taylor, 1967a: 98.
 * huonica. Ponera huonica Wilson, 1957b: 365, fig. 2 (w.q.m.) NEW GUINEA. Junior synonym of tenuis: Taylor, 1967a: 98.

Worker
Wilson (1957) Lectotype. HW 0.44 mm, HL 0.52 mm, SL 0.35 mm, CI 85, S1 80, PW 0.32 mm, petiole height 0.32 mm, petiolar node length 0.17 mm, dorsal petiole width 0.22 mm. Right mandible with three rather worn, indistinct teeth occupying the apical half of the masticatory border; followed by an indeterminate number of minute, blunt denticles occupying the basal half of the border. Eyes minute, consisting of a single ommatidium. Antennal club massive, distinctly 4-jointed, considerably longer than the remainder of the funiculus. Petiolar node seen from the side subtrapezoidal, tapering slightly dorsally, with a convex dorsal margin, its dorsal surface seen from directly above forming almost exactly a half-circle or very slightly less. Anterior half of subpetiolar process perforated by a small, median hole; the posterior apex of the process forming an acute angle.

Sculpturing as described for P. huonica Wilson.

Pilosity and pubescence as described for P. huo1llica, except that erect hairs are lacking from the occiput and pronotum; these missing hairs may well have been rubbed off in this specimen, because they are present in more recently collected material determined as tenuis.

Body uniformly yellowish brown, appendages clear yellow (specimen possibly faded; see below).

Variation in other worker series. The following measurements are based on three workers from a single nest series collected at Ebabaang : HW 0.42-0.43 mm, HL 0.49-0.52 mm, SL 0.33-0.35 mm, 01 82-86, SI 78-83, PW 0.32 mm. In these specimens the anterior half of the subpetiolar process is not perforated as in the lectotype, and the posterior angle of the process forms a right angle instead of an acute angle. The body color is uniformly blackish brown, and the appendage color is light yellowish brown; there is an excellent possibility that the considerably lighter color of the lectotype is due to fading.

Taylor (1967) - Wilson's (1957) redescription of a tenuis syntype, and his original description huonica cover general characters, but the following additional notes are pertinent:

1. Mandibular dentition varies intranidally in New Guinea samples. As usual in the genus, one observes 3 large apical teeth, followed by a series of 6-10 small denticles. In most specimens several denticles are larger than the others (usually one or 2 at about the middle of the series, and the posterior one). Minimally they are barely enlarged; maximally they are as large as the middle, or smallest, of the anterior trio of teeth. Only 2 of 30 New Guinean specimens have completely uniform denticle series. A regular row of denticles is usual in Samoan specimens, which show little tendency towards denticular heterogeniety.

2. Palpal formula: Maxillary 2: Labial 2 (3 workers each from Aiyura and Samoa dissected).

3. Dorsal mesometanotal suture totally lacking in all specimens. It is sometimes represented by a narrow, but obtuse, impression, which never breaks the underlying sculpturation.

4. Structure of the subpetiolar process shows intrademe variation as illustrated in figs. 84 and 85 (variant types labelled A-D). The varying features include depth of the process, shape of its anterior and ventral outlines, size and shape of the fenestra, and degree of development of the posteroventral teeth. There is apparent geographical variation in expression of these characters. The samples differ as follows : Huon Peninsula specimens (including the "huonica" types) range in structure from type A (fig. 84) to type B (fig. 85), most being about intermediate. The Aiyura specimens range from type B to type C (fig. 85), most being about intermediate. The Samoan specimens are even less conservative, most have structure intermediate between types C and D (fig. 85-type D is a selected maximally bizarre example). At the other extreme a few Samoan specimens have type B petioles.



Queen
Wilson (1957) - (tentative determination). HW 0.50 mm, HL 0.58 mm, SL 0.40 mm, 01 86, SI 80, dorsal petiole width 0.27 mm. Differing from the worker by the usual formicid queen-worker differences. Maximum eye length 0.15 mm. Petiolar node much thinner than in worker, seen from directly above forming much less than a half-circle. Distinguished from the queen of Ponera huonica by its larger size, darker body color (uniformly blackish brown as opposed to predominantly medium brown in huonica), and somewhat thinner petiolar node.

Taylor (1967) - Apart from slight quantitative differences queens show little variation. Wilson's 5 specimens, plus 6 from Samoa have the following dimensions: HL 0.51-0.59 mm; HW 0.43-0.51 mm; SL 0.35-0.42 mm; CI 80-86; SI 78-83; PW 0.29-0.33 mm; PNL 0.18-0.21 mm; PH 0.32-0.36 mm; DPW 0.22-0.28 mm; PNI 68-74; maximum length of compound eye 0.28-0.30 mm; ocular index 31-37; palpal formula: Maxillary 2: Labial 2 (2 speciments dissected). Agreeing with the standard plan for the genus; diagnosed by size and the 4-segmented antennal club. Wing venation of “coarctata type.”

Male
Taylor (1967) - A single male. (huonica type series), described by Wilson (1957) is typical for the genus.

Immature Forms
Taylor (1967) - Larvae have 3 pairs of glutinous abdominal tubercles. Pupae of all castes lack coccons (I have seen sufficient material to be sure that these are never spun).

Type Material
Taylor (1967) - Lemien, near Berlinhafen (=Aitape,) and Tamara I., NE New Guinea.