Polyrhachis taylori

The type series comprises the only known specimens of this species. They were collected from a nest in a bamboo stick marker in a native garden situated at the margin of primary forest. The nest occupied three adjoining internodes of the bamboo stick, with the only silk employed in its construction forming the lining of the walls and a small opening. A second nest was located under much the same circumstances nearby. (Kohout, 2014)

Identification
Polyrhachis taylori is very similar to the sympatric species Polyrhachis bellicosa and Polyrhachis erosispina. All feature similar, anterolaterally and weakly ventrally directed pronotal spines, and a virtually identical colour scheme with a black head, distinctly reddish-brown mesosoma and petiole, and a dark reddish-brown or almost black gaster in fully pigmented specimens. However, P. taylori is easily separated by its small size (HL < 1.75), which is well below the size of the smallest P. bellicosa and P. erosispina workers (HL >1.80). Also, the petiolar index in P. taylori is relatively low (PeI < 85) and the petiolar spines in most specimens are more-or-less divergent from their bases. In contrast, the petiolar index in the other two species is always higher (PeI > 85) and the petiolar spines are parallel for most of their length. (Kohout, 2014)


 * Key to the subgenus Polyrhachis workers

Distribution based on Regional Taxon Lists
Indo-Australian Region: New Guinea.

Biology
Kohout (1988) - Workers of P. taylori were first recognised foraging over felled trees in a native garden established in a clearing of primary forest. They were immediately conspicuous because of their small size. By tracking returning foragers the colony was located in a dry bamboo stick serving as a land marker, topped with a piece of black plastic sheeting. The nest occupied three adjoining internodes of the bamboo, and the only silk employed in its construction formed an ultra-thin lining on the walls of the cavities, and a small opening surrounded by the thickened bamboo node at the top, beneath the plastic cover. The colony was collected entire and comprised 639 workers (many of them callows), 16 dealate females and numerous immature stages, including eggs, small and large larvae and pupae of workers and females. A few additional specimens were collected from a second nest located under much the same circumstances in a nearby bamboo marker.

Besides P. taylori, the most common foragers in the surrounding area were the workers of Polyrhachis erosispina.

The P. taylori type-colony on the other hand contained sixteen apparently reproductive females. Unfortunately field conditions did not allow for dissection and study of ovarian condition in these individuals.

Castes
Males of this species are unknown.

Nomenclature

 *  taylori. Polyrhachis taylori Kohout, 1988b: 422, fig. 4 (w.q.) NEW GUINEA.

Worker
Dimensions (holotype cited first): TL 7.08, 6.18-7.36; HL 1.70, 1.50-1.75; HW 1.45, 1.29-1.50; CI 85, 82-87; SL 2.21, 1.93-2.34; SI 152, 146-159; PW 0.76, 0.67-0.78; MTL 2.93, 2.56-3.06; PeH 1.40, 1.15-1.50; PeI 82, 77-85 (50 measured).

Mandibles with 5 teeth progressively shorter towards the base. Clypeus convex in profile, not carinate. Sides of head in front of eyes almost straight, converging anteriorly, rounded behind the eyes. Antennal carinae sinuate, the area between them rather flat, with a weakly defined median longitudinal carina. Antennal scapes exceeding occipital border by approximately half their length. Eyes moderately convex, in full face view breaking the outline of the head. Median ocellus present; lateral ocelli obscure, sometimes lacking. Pronotal dorsum slightly convex in side view; the spines long and acute, projecting antero-laterally, with the tips gently downcurved; outer borders of spines each continuous basally with the rather ill-defined pronotal margin, which terminates at a distinct posteriolateral angle near the promesonotal suture. The latter clearly impressed on the mesosomal dorsum. Mesonotum convex, bearing a pair of pyramidal, rather compressed, posterodorsally projecting spines, with laterally curved tips. Metanotal groove indistinct. Propodeal dorsum weakly margined on each side, the margins terminating posteriorly as medially directed short transverse ridges which partially separate the basal and declivitous faces. Declivity abrupt, shorter than the dorsal face. Petiole columnar, bearing a pair of hookshaped, transversally flattened spines, more or less divergent from their bases. Gaster eliptical, with first tergite covering less than half the dorsum.

Mandibles shining, finely longitudinally striate-punctate. Head feebly shining, closely reticulate-punctate, with sides less densely sculptured than dorsum. Mesosoma and petiole generally reticulate-punctate, somewhat irregularly reticulate-striate laterally; sculptural intensity reduced on the pronotal disc, which is fairly smooth and shining. Gaster moderately shining, very finely shagreened.

Mandibles, anterior clypeal margin, coxae, subpetiolar process and gaster with sparse, moderately long, sub-erect yellowish hairs. Eyes with numerous short erect hairs. Appressed to suberect, short, off-white pubescence abundant on entire body and appendages, without obscuring the underlying sculpturation.

Mandibles, head, antennae, tips of spines, tibiae and tarsi black. Body of mesosoma, petiole, coxae and femora (save for their apical portions) light reddish-brown. Gaster dark reddish-brown, with the base widely diffused with medium reddish-brown colouration. Posterior margins of tergites narrowly black.

Queen
Dimensions: TL 8.92-9.47; HL 1.92-1.96; HW 1.43-1.48; CI 73-76; SL 2.71-2.82; SI 185-196; PW 1.18-1.26; MTL 3.43-3.65; PeH 0.94-1.06; PeI 49-54 (16 measured).

Very different from the worker; and with the characters identifying full sexuality – complete thoracic structure and ocelli.

Mandibles with four teeth; the apical tooth 3x longer than those following, which are subequal in length. Clypeus convex in profile, the median portion strongly produced, anterior margin entire, posterior suture distinct, impressed medially, slightly elevated laterally and terminating as a short ridge at the base of the mandible. Sides of the head in front of eyes feebly to distinctly concave, virtually parallel; the cephalic outline strongly converging behind the eyes. Antennal carinae well elevated, more so than in worker; area between them gently concave, with a median longitudinal carina. Antennal scapes extending beyond occipital border by half their length. Eyes relatively large, convex. Pronotum with a pair of short, antero-laterally projecting spines. Mesoscutum quite high anteriorly, with a flat dorsal surface; median line terminating dorsally in a shallow depression; parapsides slightly elevated posteriorly. Mesoscutellum convex, transverse. Propodeal dorsum not marginate, sloping posteriorly to the declivity in an even, medially unbroken curve; posterior angles produced into upturned, medially separated transverse ridges, which do not meet at the midline. Petiole with antero-dorsal face concave, bearing a pair of slender, relatively long, widely diverging spines. Gaster elongated, elliptical.

Mandibles finely longitudinally striate-punctate, with numerous piliferous pits. Clypeus finely punctate. Head reticulate-punctate, the sculptural intensity increasing to coarse on vertex and occiput; moderately shining. Mesosoma and petiole reticulate-punctate, sculptural intensity increasing dorsally, with mesoscutum subopaque. Gaster microscopically reticulate-punctate, moderately shining.

Pilosity very sparse, consisting of short to medium long, sub-erect yellow hairs on mandibles, anterior clypeal margin, posterior faces of anterior coxae, subpetiolar process and posterior margins of terminal gastric tergites and sternites. Very short, fine, appressed yellow pubescence abundant all over the body and appendages.

Mandibles reddish-brown, bordered with black. Head and body largely black, with a reddish-brown cast on the neck, lateral portions of pronotum and on sides of petiole below stigma, except subpetiolar process, which is black. Antennal scapes, coxae, femora and tibia medium reddish-brown, somewhat infuscated dark brown, with femora a shade lighter; tarsi black. Gaster black with lateral margins of tergites and sternites infuscated dark reddish-brown.

Immatures
Eggs off-white, elongate-elliptical, 0.31-0.34 X 0.81-0.87 mm. Larvae with long, hook-terminated hairs. Pupae enclosed in cocoons. P. taylori is easily recognisable by its small stature (HL < 1.75), which is well below the size of the smallest known bellicosa and erosispina specimens (HL > 1.80). The petiolar index in taylori is relatively low (PeI < 85) and the spines are more or less divergent from their bases. In bellicosa and erosispina the petiolar index is always higher (PeI > 85) and the spines are parallel for most of their length. These two species are common and widespread throughout Papua New Guinea, but P. taylori is known only from its type locality.

Type Material
HOLOTYPE: PAPUA NEW GUINEA, WEST SEPIK PROV.: Torricelli Mts., Lumi, 400-550m, 03.28 S X 142.02 E, 4-13 August 1984, RJK acc. 84.247.

PARATYPES: data as for holotype (638 nidoparatype workers, 16 nidoparatype dealate females and immature stages - eggs, larvae in various stages of development and pupae of workers and females); ditto, RJK acc. 84.249 (8 paratype workers).

Holotype, most nidoparatypes, 4 paratypes and immature stages in (Type no. 7731); 10 nidoparatypes (8 workers, 2 females) and 4 paratypes in RJK; 4 nidoparatypes (3 workers, 1 female) in ; 2 nidoparatype workers each to, , , , , , , , , 🇿🇲, ,.