Polyrhachis retrorsa

Specimens have been collected from fogging samples in natural forest and within an elevation range of 400-1080m.

Identification
A member of the Polyrhachis mucronata  species group.

Kohout (2008) - Polyrhachis retrorsa bears a very close resemblance to Polyrhachis mitrata from the Philippines but direct comparison of the types of both species supports their separate specific status. Polyrhachis mitrata has a narrower mesosoma with the pronotal humeri angular and the propodeal and petiolar spines distinctly more slender. The petiole in lateral view has a weakly convex anterior face, an almost straight posterior face and a rather narrow dorsum that bears a pair of minute, posteriorly directed, intercalary teeth. Polyrhachis mitrata is black with the legs and gaster medium reddish-brown and the antennae a shade darker and the body is covered with whitish pubescence that is rather diluted, notably on dorsum of the head, mesosoma and gaster. However, the syntype examined appears to be a worn specimen. In contrast, the pronotal humeri in P. retrorsa are unarmed and widely rounded and the propodeal spines shorter and broader at their bases. In profile, both faces of the petiole are convex and only slightly converge towards the widely rounded dorsum. The petiole generally lacks intercalary teeth, although rudimentary teeth are evident beneath the pubescence in a few specimens. Polyrhachis retrosa is black with reddish-brown appendages and has relatively long, appressed, silvery-grey pubescence that clearly distinguishes the species from the other, mostly jet black members of the mucronata-group.

Distribution based on Regional Taxon Lists
Indo-Australian Region: Indonesia.

Nomenclature

 *  retrorsa. Polyrhachis retrorsa Emery, 1900d: 719 (w.q.) INDONESIA (Mentawei I.). Combination in P. (Myrmhopla): Emery, 1925b: 196.

Type Material
Kohout (2008) - Syntype worker, queens. INDONESIA, Mentawei I., Sipora, Sereinu (E. Modigliani), (examined).

References based on Global Ant Biodiversity Informatics

 * Chapman, J. W., and Capco, S. R. 1951. Check list of the ants (Hymenoptera: Formicidae) of Asia. Monogr. Inst. Sci. Technol. Manila 1: 1-327
 * Emery, C. "Formiche raccolte da Elio Modigliani in Sumatra, Engano e Mentawei." Annali del Museo Civico di Storia Naturale Giacomo Doria (Genova) (2) 20, no. 40 (1900): 661-722.
 * Kohout, R. J. 2008. A review of the Polyrhachis ants of Sulawesi with keys and descriptions of new species (Hymenoptera: Formicidae: Formicinae). Memoirs of the Queensland Museum 52:255-317.
 * Robson Simon Database Polyrhachis -05 Sept 2014