Polyrhachis johnsoni

Mann (1919) reported a colony was found in a silk and carton nest on a palm leaf.

Identification
Polyrhachis johnsoni was originally described as a variety of Polyrhachis rastellata, but was treated by Donisthorpe (1938) as a variety of Polyrhachis debilis. Polyrhachis johnsoni is certainly more closely related to Polyrhachis debilis than to Polyrhachis rastellata but can be easily distinguished from both by the outline of pronotum. In Polyrhachis johnsoni the pronotal dorsum is rather flat, while it is distinctly convex in the other two species. From Polyrhachis rastellata it also differs by the presence of distinct, though short, propodeal spines or tubercles. From Polyrhachis debilis it differs primarily by its distinctly larger size (HL 1.72-1.87 in Polyrhachis johnsoni syntypes versus 1.34-1.47 in Polyrhachis debilis syntypes) and by the propodeal declivity that is almost as high as the full height of the petiole. In Polyrhachis debilis the propodeal declivity is relatively low, with its dorsal margin barely reaching the level of the bases of the dorsal petiolar teeth. (Kohout 2006)

Distribution
The known distribution of Polyrhachis johnsoni appears to be limited the Solomon Islands, but there are a few unconfirmed records from the East Britain Province of Papua New Guinea. (Kohout 2006)

This taxon was described from Solomon Is.

Nomenclature

 *  johnsoni. Polyrhachis (Cyrtomyrma) rastellata var. johnsoni Mann, 1919: 390 (w.) SOLOMON IS. Subspecies of debilis: Donisthorpe, 1938c: 266. Raised to species: Kohout, 2006b: 140.

Worker
Length 7 mm.

Resembling laevior var. debilis Emery in having on the epinotum a pair of distinct though very short and small spines. It is much larger in size than debilis and the legs are uniformly dark brown, almost black. The thorax is evenly arched, much as in leonidas Forel and the epinotal declivity in profile is straight.

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

Type Locality Information
SOLOMON IS., Rendova, col. W.M. Mann.