Polyrhachis debilis

Donisthorpe (1938): "taken in a nest of leaves woven together with silk at Mafulu, 4000 ft., Papua by Miss L. E. Cheesman, xii. 1933. Miss Cheesman swept off herbage a number of workers of the same species at Kokoda." Nothing more is known about the biology of Polyrhachis debilis.

Identification
Polyrhachis debilis is similar to Polyrhachis yorkana. Both species both display considerable variability in the development of the propodeal spines which range from inconspicuous tuberculae to short spines. However, they differ in numerous characters, including the shape of the head, which in P. debilis is as wide or even wider than long (CI 100-103), while in P. yorkana it is distinctly longer than wide (CI 96-98). In full face view, the eyes of P. debilis do not reach the sides of the head, while in P. yorkana they clearly break the cephalic outline. In lateral view, the pronotum is distinctly convex in P. debilis and rather ﬂat in P. yorkana. In dorsal view, the pronotum in P. debilis is relatively narrow with evenly rounded shoulders, while in P. yorkana the pronotum is distinctly widest just behind the shoulders and, in the majority of specimens examined, the pronotal humeri are subangular or distinctly angular. They also differ in their relative size, with P. debilis distinctly smaller (HL 1.34-1.47 verus HL 1.56-1.62). (Kohout 2006)

Distribution
Papua New Guinea to the islands of eastern Indonesia.

Polyrhachis debilis previously recorded from Australia (Kohout, 2000) belong to Polyrhachis yorkana. Although the type locality of Polyrhachis debilis (Fly River, Papua New Guinea) is situated just across Torres Strait from Cape York Peninsula, it apparently does not occur in Australia. (Kohout 2006)

This taxon was described from New Guinea.

Worker
Differisce dal tipo della P. laevior per le spinette del metanoto ridotte a piccolo denti, talvolta appena sensibili. Sono nel dubbio se riferirla alla P. laevior o alla rastellata, perche connette intimamente le due forme; percio credo che la P. laevior debba essere considerate come razza della rastellata.

Queen
Similar to worker, but the shoulders are more rounded,the teeth of the epinotum reduced to small tubercules, those of the scale blunter. Wings yellowish; pterostigma and veins light yellowish brown. (Donisthorpe 1938).

Male
Donisthorpe (1938) reported males were taken with a nest series but this caste remains undescribed.

Type Material
Syntype workers, , , – as reported by Kohout (2006).

Type Locality Information
NEW GUINEA, Fly River, col. L.M. D’Albertis; INDONESIA, Aru Island, col. O. Beccari.

Additional References
Emery, E. 1887. Catalogo delle formiche esistenti nelle collezioni del Museo Civico di Genova. Parte terza. Formiche della regione Indo-Malese e dell’ Australia. Annali del Museo Civico di Storia Naturale di Genova 4(2):209-258.

Kohout, R. J. 2000. A review of the distribution of the Polyrhachis and Echinopla ants of the Queensland Wet Tropics (Hymenoptera: Formicidae: Formicinae). Memoirs of the Queensland Museum 46: 183-209.

Kohout, R. J. 2006. Review of Polyrhachis (Cyrtomyrma) Forel (Hymenoptera: Formicidae: Formicinae) of Australia, Borneo, New Guinea and the Solomon Islands with descriptions of new species. Memoirs of the Queensland Museum. 52:87-146.