Polyrhachis delecta

Polyrhachis delecta build their nests between the leaves of trees and shrubs (Kohout 2006). Larval silk and carton are used to secure the nests (Tranter & Hughes 2015).

Identification
Remarkably similar to Polyrhachis euryala from Indonesia. Both are distinctly slender with a relatively narrow mesosoma and widely rounded pronotal shoulders. However, P. delecta has distinctly shorter antennal scapes (SI 119-129 versus 140-147 in P. euryala) and subequal petiolar spines. In P. euryala the lateral petiolar spines are distinctly longer than the dorsal pair. (Kohout 2006)

Distribution
Rainforests of Queensland’s Wet Tropics.

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Abundance
Common

Biology
Tranter & Hughes (2015) studied three nests formed from five or fewer leaves at the terminus of a hanging branch, with the leaves slightly folded and woven together with silk and carton material. All nests had one entrance located at the bottom of the nest. Internally, nests were composed of one or two large chambers, and a number of smaller chambers towards the periphery. These chambers were lined with silk sheets. They described the construction of silk ‘girder’ structures which spanned larger chambers, and hypothesized that these provide additional strength to the internal nest structure. Colonies consisted of one dealate queen, 421, 465 and 216 workers, as well as dozens of brood

Castes
Males (undescribed) and immature stages (eggs, larvae and pupae) deposited in the spirit collection. (Kohout 2006)

Nomenclature

 *  delecta. Polyrhachis delecta Kohout, 2006b: 97, figs. 2A, D-E (w.q.m.) AUSTRALIA.

Worker
Dimensions (holotype cited ﬁrst): TL c. 6.35, 5.90-6.50; HL 1.62, 1.47-1.62; HW 1.59, 1.40-1.59; CI 98, 93-100; SL 1.90, 1.81-1.96; SI 119, 119-129; PW 1.25, 1.15-1.28; MTL 2.31, 2.09-2.37 (25 measured).

Clypeus in proﬁle rounding into shallowly impressed basal margin in weakly convex line. Frontal triangle rather indistinct. Frontal carinae sinuate with moderately raised margins; central area with moderately impressed frontal furrow. Sides of head in front of eyes very weakly convex; behind eyes rounding into convex occipital margin. Eyes moderately convex, in full face view just breaking lateral cephalic outline. Ocelli lacking. Pronotal humeri in dorsal view widely rounded; greatest width of pronotum at mid-length of segment. Mesosoma in proﬁle evenly convex; promesosonal suture distinct; metanotal groove lacking, position indicated by slight depression in mesosomal outline; propodeal dorsum narrowly rounding into rather steep declivity. Petiole with anterior face almost straight, posterior face convex; dorsal margin armed with four acute, subequal spines. Subpetiolar process angular anteriorly, blunt posteriorly. Anterior face of ﬁrst gastral segment relatively low, widely rounding onto dorsum of segment.

Mandibles very ﬁnely, longitudinally rugose. Dorsum of head, mesosoma and gaster ﬁnely shagreened with intensity of sculpturation increasing laterally, sides of mesosoma and petiole strongly reticulate-rugose. All dorsal body surfaces, including mandibles, with numerous minute punctures and piliferous pits.

Several curved and semierect hairs arising from mandibular masticatory borders. Anterior clypeal margin usually with 3 longer, anteriorly directed setae and fringe of shorter setae lining margin laterally. Several paired, medium length, hairs near anterior and basal clypeal margins and along frontal carinae; a pair of somewhat longer hairs on vertex. Tuft of a few, weakly curved hairs, shorter than greatest diameter of eye, on summit of mesonotum. Medium length hairs lining posterior margins of gastral segments, more numerous on venter. Colour. Black, including antennae, coxae and tarsi. Mandibular masticatory borders, extreme tip of apical funicular segments, condylae and posterior margins of gastral segments reddish-brown. Femora and tibiae light to medium reddish-brown, except proximal ends of tibiae distinctly darker.

Queen
Dimensions: TL c. 7.26-8.06; HL 1.72-1.78; HW 1.65-1.68; CI 93-98; SL 2.03-2.09; SI 121-127; PW 1.81-1.93; MTL 2.56-2.71 (6 measured). Apart from sexual characters, similar to worker except: eyes larger, in full face view clearly breaking cephalic outline. Pronotal humeri narrowly rounded; mesoscutum marginally wider than long; lateral margins converging anteriorly, forming relatively widely rounded anterior margin; median line bifurcated posteriorly; parapsides weakly indicated, slightly raised posteriorly; mesoscutum in proﬁle with relatively high, widely rounded anterior face and ﬂat dorsum. Mesoscutellum in proﬁle convex, weakly elevated above dorsal plane of mesosoma; metanotal groove distinct. Propodeal dorsum descending into virtually vertical declivity. Petiole with spines shorter and blunter. Sculpturation and colour pattern essentially as in worker.

Type Material
HOLOTYPE: QUEENSLAND, Palmerston NP, 17°37’S, 145°48’E, c. 400m, 4.v.1997, primary rf, S.K.A. Robson acc. #551 (worker). PARATYPES: data (and nest) as for holotype (294 workers, 1 dealate queen, 67 alate queens, 77 males). Holotype (QMT99335), paratype dealate queen, most paratype workers, alate queens and males in ; 3 paratype workers and 1 paratype alate queen each in, and ; 2 paratype workers each in , , , ,  and.