Polyrhachis semitestacea

Identification
As mentioned by (Kohout, 1998), P. semitestacea is rather similar to Polyrhachis andromache Roger, with relatively subtle differences separating them. However, these differences appear constant and serve to clearly separate the species. The most obvious difference is the colour of the gaster which is honey-yellow in P. semitestacea and contrasts with the dark mesosoma, while in P. andromache the gaster is black and concolorous with the rest of the body. When directly compared, P. semitestacea is distinctly more slender and has a petiole armed with more closely spaced spines and lacking a dorsal intercalary tooth. In contrast, P. andromache appears more robust, has more widely spaced petiolar spines and the dorsal edge of petiole is armed with a minute intercalary tooth. (Modified from Kohout, 2012.)

Distribution based on Regional Taxon Lists
Indo-Australian Region: Papua New Guinea.

Nomenclature

 *  semitestacea. Polyrhachis andromache var. semitestacea Emery, 1900c: 334 (w.) NEW GUINEA. Combination in P. (Myrma): Emery, 1925b: 202. Raised to species: Kohout, 1998: 524. See also: Kohout, 2012: 36.

Lectotype and paralectotype workers (designated by Kohout, 2012: 36) from Friedrich-Wilhelmshafen (= Madang), New Guinea, L. Biró (examined by Kohout, 2012).

Note: The lectotype was selected from 25 available syntypes lodged in the Biró collection (HNHM). The specimen is card mounted and in good condition. It bears the following printed labels: ‘N. Guinea, Biró 96’ and ‘Friedrich-Wilh.-hafen’. In addition it also bears an original name-tag in Emery’s handwriting, reading ‘Polyrhachis andromache Rog. var. semitestacea Emery’. It has been furnished with an additional tag indicating its new status, with the remaining 24 specimens deemed paralectotypes and labelled appropriately. Two of the paralectotypes were generously donated to the QM collection (Kohout, 2012).

Description
Queen. (Described by Kohout, 2012.) Dimensions: TL c. 10.53-10.89; HL 2.62-2.72; HW 2.07-2.17; CI 79-80; SL 3.02-3.12; SI 144-146; PW 2.02-2.17; MTL 3.28-3.33 (2 measured). Apart from sexual characters, very closely resembling worker. Pronotal humeri armed with moderately long, acute and weakly downturned spines; their dorsolateral margins continued posteriorly only for a short distance. Mesoscutum wider than long with lateral margins converging anteriorly into moderately rounded anterior margin; median line well indicated, relatively short; parapsides rather flat; mesoscutum in profile relatively low with anterior margin rounding onto weakly convex dorsum; mesoscutellum weakly convex, only marginally elevated above dorsal plane of mesosoma. Propodeal dorsum with lateral margins rounded posteriorly and continued inwards for a short distance, but not meeting; dorsum descending rather abruptly into vertical declivity. Petiole armed with two short, somewhat flattened, blunt spines and distinct intercalary tooth. Sculpturation, pilosity and colour virtually as in worker.

Additional References

 * Kohout, R.J. 2012. A review of the Australian Polyrhachis ants of the subgenera Myrma Billberg, Myrmatopa Forel, Myrmothrinax Forel and Polyrhachis Fr. Smith (Hymenoptera: Formicidae: Formicinae). Memoirs of the Queensland Museum – Nature 56(1): 25-59.