Polyrhachis decemdentata

The nests of decemdentata are usually constructed in rotten parts of standing trees, often a considerable distance above the ground. Branches which have previously suffered termite attack appear to be preferred, but the species has been recorded in Ghana nesting in the stump of a fallen cocoa tree. The species is arboreal and very rarely comes to ground level; it is apparently tolerated in trees by dominant species of the genera Oecophylla and Crematogaster. (Bolton 1973)

Identification
A member of the Polyrhachis militaris species-group.

Bolton (1973) - The presence of six spines or teeth on the petiole distinguishes this species from all others in the regional fauna except Polyrhachis andrei, which is known only from the female.The female closely resembles P. andrei, the characters for their separation are given under that species.

The varieties and subspecies in synonymy were mostly founded upon quite trivial variations in colouration or in sculptural intensity. Material examined embraces all the described infraspecific forms, with numerous intermediates, and places the previously described forms well within the limits of variation of the species. The limits in sculptural reduction are perhaps best shown by a female in the BMNH collection, from Uganda. In this specimen the mesoscutum is devoid of sculpturation except for a faint superficial reticulation; the scutellum and the propodeal dorsum are weakly reticulate-rugose and the whole body is very shiny.

Distribution based on Regional Taxon Lists
Afrotropical Region: Cameroun, Congo, Equatorial Guinea, Gabon, Ghana, Guinea, Ivory Coast, Nigeria, Sierra Leone, Uganda.

Biology
Bolton (1973) - Alate females of Polyrhachis decemdentata have been recorded as follows. GHANA : October. NIGERIA : March, July, August. SIERRA LEONE : August. UGANDA: August, December.

Nomenclature

 *  decemdentata. Polyrhachis decemdentata André, 1889: 219 (w.) SIERRA LEONE. Emery, 1892d: 567 (q.); Forel, 1915c: 351 (m.). Combination in P. (Myrma): Forel, 1916: 450. Senior synonym of fernandensis, flavipes, gustavi, tenuistriata: Bolton, 1973b: 302.
 * fernandensis. Polyrhachis decemdentata var. fernandensis Forel, 1901e: 377 (w.) EQUATORIAL GUINEA. Santschi, 1910c: 396 (q.). Junior synonym of decemdentata: Bolton, 1973b: 302.
 * flavipes. Polyrhachis decemdentata var. flavipes Stitz, 1910: 149 (w.q.) CAMEROUN. Junior synonym of decemdentata: Bolton, 1973b: 302.
 * gustavi. Polyrhachis (Myrma) decemdentata var. gustavi Emery, 1921e: 22 (q.) EQUATORIAL GUINEA (Bioko I.). Junior synonym of decemdentata: Bolton, 1973b: 302.
 * tenuistriata. Polyrhachis (Myrma) decemdentata subsp. tenuistriata Menozzi, 1933a: 114 (w.) UGANDA. Santschi, 1937g: 85 (q.). Junior synonym of decemdentata: Bolton, 1973b: 302.

Worker
Bolton (1973) - TL 4.7-6.7, HL 1.18-1.59, HW 1.07-1.48, CI 87-93, SL 1.15-1.55, SI 105-114, PW 0.85-1.33, MTL 1.22-1.74. (28 measured)

Anterior clypeal margin arcuate, convex to shallowly concave medially. Eyes convex, moderately protuberant. Sides of head in front of eyes convex and convergent anteriorly; behind the eyes the sides round into the very shallowly convex occipital margin. Alitrunk marginate throughout its length, the margination interrupted at the sutures. All dorsal surfaces transversely convex, the propodeum somewhat more markedly so than the pronotum or mesonotum. Pronotum armed with a pair of broad, flattened, triangular spines; propodeum with a pair of short upcurved spines or teeth. Promesonotal suture distinct; metanotal groove developed and deeply impressed. Petiole with six spines or teeth; a lateral pair of long spines directed upwards and weakly backwards, a dorsal pair of broad, acute teeth which are usually short and dentiform but occasionally projecting as distinct spines, and a pair of teeth or short spines situated below and behind the long lateral spines and directed backwards and upwards. The last mentioned pair are sometimes reduced to small tubercles. Anterior face of first gastral segment concave medially.

All dorsal surfaces of the body and appendages with numerous erect hairs, white or yellowish in colour. Pubescence sparse, grey or off-white.

Sculpturation variable, usually with the head and the dorsum of the alitrunk finely longitudinally rugose or striate-rugose with shining or weakly reticulate-punctate interspaces. Sometimes the sculpture is very much effaced or more distinctly reticulate-rugose, especially on the dorsum of the alitrunk. On the propodeal dorsum the rugae may be transverse or, in some individuals, diagonal. Gaster usually finely and densely reticulate-punctate but with all intergrades to the possession of a fine superficial reticulation only. Colour black, often entirely so but sometimes the legs (especially the fore tibiae) lighter, brown or yellow-brown.

Queen
Bolton (1973) - As worker, answering to the above description except in the structure of the alitrunk. The pronotal spines are reduced and the sculpturation of the scutellar dorsum is usually distinctly reticulate-rugose.

Type Material
Bolton (1973) - Holotype worker, SIERRA LEONE.