Polyrhachis abbreviata

Builds its nests of larval silk and vegetation debris between the leaves of rainforest trees and shrubs. (Kohout, 2006)

Identification
Kohout (2006): Polyrhachis abbreviata is rather similar to Polyrhachis yorkana with which it is sympatric at Mission Beach. They differ notably in their size (HL 1.25-1.34 in P. abbreviata versus 1.53-1.62 in P. yorkana) and in the colour of their appendages which, in P. abbreviata, are yellow, orange or light reddish-brown. In contrast the legs in P. yorkana are brown to dark reddish-brown. Also, the petiole in profile is distinctly lower and wider in P. abbreviata compared to P. yorkana.

Distribution
Queensland’s Wet Tropics.

This taxon was described from Australia.

Abundance
Relatively rare.

Castes
The male of Polyrhachis abbreviata is unknown.

Worker
Dimensions (holotype cited first): TL c. 4.84, 4.68-5.49; HL 1.31, 1.25-1.34; HW 1.22, 1.15-1.28; CI 93, 90-98; SL 1.56, 1.53-1.65; SI 128, 124-133; PW 0.94, 0.94-1.00; MTL 1.78, 1.72-1.87 (20 measured).

Clypeus in profile weakly convex; basal margin moderately impressed. Frontal triangle indistinct. Frontal carinae sinuate, margins weakly raised; central area with short furrow. Sides of head in front of eyes very weakly convex, almost straight, strongly converging towards mandibular bases; behind eyes sides rounding into convex occipital margin. Eyes convex, in full face view breaking lateral cephalic outline. Ocelli lacking, relative positions indicated in some specimens by minute depressions in cephalic sculpturation. Pronotum in dorsal view with humeri narrowly rounded, or bluntly angular in some specimens, with greatest width of segment just behind shoulders. Mesosoma in profile more-or-less evenly convex. Promesonotal suture distinct, metanotal groove feebly indicated laterally, indistinct dorsally. Propodeal spines very short, upturned. Petiole in lateral view with anterior face almost straight, posterior face convex; dorsum armed with four spines; dorsal pair triangular, tooth-like, closer to each other than to lateral teeth; lateral pair more acute and slightly longer; subpetiolar process in lateral view acute anteriorly, narrowly rounded posteriorly. Anterior face of first gastral segment relatively low, widely rounding onto dorsum of segment.

Mandibles finely, longitudinally striate-rugose. Dorsum of head, mesosoma, petiole and gaster very finely shagreened, rather polished, with scattered minute puctures and piliferous pits. Sculptural intensity increasing laterally and becoming rather strongly reticulate-rugose, notably on meso- and metapleurae and lower parts of petiole.

Several curved hairs along mandibular masticatory borders with hairs reducing in length towards bases. Anterior clypeal margin with only 1 or 2, relatively long, anteriorly directed setae medially and a few shorter setae fringing margin laterally. A few pairs of medium length, mostly erect hairs near anterior and basal clypeal margins and along frontal carinae; single pair of hairs on vertex and summit of mesosoma. Gaster with a few erect hairs along posterior margins of segments, notably towards apex and on venter. Head, mesosoma, petiole and gaster with very short, appressed pubescence arising from numerous pits and shallow punctures.

Colour. Body black. Mandibular masticatory borders reddish-brown. Antennae very dark brown, condylae and distal ends of scapes a shade lighter. Legs distinctly yellow, orange or reddish-brown, with coxae and proximal ends of tibiae a shade darker; tarsi very dark brown.

Queen
Queen. Dimensions: TL c. 7.21; HL 1.72; HW 1.56; CI 91; SL 1.93; SI 124; PW 1.62; MTL 2.40 (1 measured). Apart from sexual characters and distinctly larger size, closely resembling worker except: pronotal humeri rounded; mesoscutum only marginally wider than long with lateral margins rather strongly converging anteriorly, forming distinctly narrowly rounded anterior margin. Median line relatively short; parapsides rather flat, slightly raised posteriorly; mesoscutum in profile weakly convex anteriorly, virtually flat posteriorly. Mesoscutellum convex in lateral view, well elevated above dorsal plane of mesosoma; metanotal groove distinct. Propodeum armed with distinct, somewhat dorsoventrally compressed, weakly upturned spines; dorsum descending rather abruptly into virtually vertical declivity; petiolar spines marginally longer. Sculpturation, pilosity and colour as in worker.

Immature Stages
Eggs, larvae and pupae deposited in the spirit collection.

Type Material
Holotype (QMT99331), most paratype workers and paratype queen in ; 2 paratype workers each in, , , , , , , and.

Type Locality Information
HOLOTYPE: QUEENSLAND, Mission Beach, c. 4km WbyS of, 17°53’S, 146°04’E, 29.ii.1996, lowland rf., ex silk nest between leaves, S.K.A. Robson #253 (worker). PARATYPES: data (and nest) as for holotype (157 workers, 1 dealate queen).