Polyrhachis delicata

This species is an arboreal nester, using silk to join the leaves of various lowland rainforest trees and shrubs (Kohout 1999, 2000; Robson & Kohout 2005, 2007; Kohout, 2012).

Identification
As indicated by Kohout (1994), the most obvious differences between P. delicata and Polyrhachis queenslandica are their colour and the orientation of their propodeal spines. However, due to a high degree of variability, notably within Queensland populations of both species, these characters can be unreliable and, while both species are usually separable, no single character is universally diagnostic. The propodeal spines in P. delicata are generally more strongly upturned, but the actual angle of elevation varies between specimens, even those of the same nest series. The propodeal spines in P. queenslandica are distinctly less elevated with only a small amount of variation between the specimens examined. The colour of the body appears to be a more reliable character to separate the species but only in fully pigmented specimens. A mostly red or reddish-brown mesosoma, gaster and appendages, contrasting with a darker head (almost black in some specimens) characterises P. delicata, while the body in P. queenslandica is mostly uniformly black or very dark reddish-brown. The sculpturation of the head and mesosoma in P. delicata is rather distinctly reticulate-punctate and opaque, while it is markedly more finely and closely punctate in P. queenslandica. The petiolar node in P. delicata is relatively slim and distinctly narrows dorsally in lateral view, with the anterior face smoothly curving onto the petiolar dorsum in an uninterrupted line that incorporates the anterior edge of the dorsoposteriorly elevated median spine. In contrast, the petiolar node in P. queenslandica is distinctly thicker in lateral view, with the anterior face curving onto a virtually flat dorsum and the median petiolar spine dorsoposteriorly elevated at a distinctly steeper angle. The latter character does not serve to separate the queens of the two species, however, the median petiolar spine in the queen of P. queenslandica is simply pointed, while its apex is clearly emarginated in P. delicata.

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Polyrhachis delicata is known from two disjunct populations, one in the Northern Territory around Darwin and the other in northern Queensland, ranging from about Coen on Cape York Peninsula south to Cairns. The specimens of the type series of the junior synonym P. lysistrata were allegedly collected ‘near Townsville’ by F.P. Dodd on 30.iv.1902, however, I have seen no other specimens of this species collected that far south.

Castes
Males and immature stages (eggs, larvae and pupae) in QM spirit collection. (Kohout 2012)

Nomenclature

 *  delicata. Polyrhachis delicata Crawley, 1915b: 238 (w.) AUSTRALIA. Kohout, 2012: 51 (q.). Junior synonym of queenslandica: Crawley, 1921: 96. Revived from synonymy and senior synonym of lysistrata: Kohout, 1994a: 135.
 * lysistrata. Polyrhachis (Myrmothrinax) lysistrata Santschi, 1920a: 569 (w.) AUSTRALIA. Junior synonym of delicata: Kohout, 1994a: 135.

Polyrhachis delicata type material.

Syntype workers from Darwin, Northern Territory, Australia, 16.iv.1913 (G.F. Hill) (examined by Kohout, 2012).

Polyrhachis lysistrata type material.

Syntype workers from Townsville, Queensland, Australia (F.P. Dodd) (examined by Kohout, 2012).