Pristomyrmex mandibularis

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

Nomenclature

 *  mandibularis. Pristomyrmex mandibularis Mann, 1921: 444 (w.) FIJI IS. Sarnat & Economo, 2013: 54 (q.m.). See also: Wang, M. 2003: 505.

Description
The following from Sarnat & Economo (2013):

Alate queen. Measurements (n = 10): TL 3.22–3.65, HW 0.80–0.86, HL 0.77–0.85, CI 99–106, SL 0.64–0.74, SI 79–88, EL 0.14–0.18, PW 0.61–0.67, ML 0.82–0.96, PeH 0.22–0.26, PeL 0.14–0.18, PeI 58–76, PpH 0.26–0.29, PpL 0.16–0.19, PpI 59–69.

Measurements of aberrant specimen CASENT0194557: TL 4.10, HW 1.01, HL 0.96, CI 105, SL 0.77, SI 77, EL 0.19, PW 0.76, ML 1.06, PeH 0.30, PeL 0.17, PeI 58, PpH 0.32, PpL 0.21, PpI 65.

Conforming to the generic Pristomyrmex definition detailed in Wang (2003) with the following specifications. Closely resembling worker in the structure of the mandibles, clypeus, petiole, postpetiole and gaster in addition to sculpture, color and pilosity with the following differences. Distinctly larger. Eyes much larger with diameter composed of ca. 12 facets. Three ocelli present. Posterior head margin flat to weakly concave. Median clypeal tooth distinct to nearly absent. Mesosoma marked with wing sclerites and dorsal sutures. Propodeal spines significantly smaller than those of worker; present as large and broad distinct angles approximately equal in size to propodeal lobes. Dorsum of head entirely free of foveae to covered in abundant well-defined foveae. Dorsum of mesosoma with more than 10 pairs of erect hairs.

Male. Measurements (n = 21): TL 2.55–3.22, HW 0.51–0.61, HWE 0.63–0.75, HL 0.48–0.6, CI 97–113, SL 0.14–0.21, SI 26–34, EL 0.21–0.25, PW 0.53–0.73, ML 0.8–1.08, PeH 0.14–0.19, PeL 0.27–0.38, PeI 178–234, PpH 0.18–0.23, PpL 0.13–0.17, PpI 64–83.

Conforming to the generic Pristomyrmex definition detailed in Wang (2003) with the following specifications. Head, including the eyes, broader than long. Dorsal portion of occipital margin raised into a transverse carina from which no short lengths of longitudinal carinae originate. Frontal carina weak, terminating before reaching the posterior level of the eye. Clypeus with a median longitudinal carina and 1–3 pair of lateral carinae extending towards the anterior margin. Anterior clypeal margin flat to weakly convex. Mesoscutum with distinct notauli forming a Y-shape. Parapsidal furrows reduced to weak impressions. Scuto-scutellar sulcus with 7–10 narrow longitudinal ridges visible in dorsal view. Propodeum armed with a pair of strong tubercles or small teeth. Propodeal lobes obtusely triangular with a blunt or rounded apex; usually more developed than propodeal teeth. Middle and hind tibiae lacking spurs. Petiole in profile cuneiform with a weakly developed and broadly convex node. Peduncle long. Postpetiole in profile nodiform with a steeply convex anterior face and shorter, more gently sloped posterior face. In dorsal view subrectangular and broader than long. Entirely smooth and shiny. All dorsal surfaces with abundant long erect to suberect hairs. Legs and scapes with numerous erect or suberect short hairs. Color black to blackish brown with lighter brown appendages and gaster. Wings infuscated.

Geographic variation. Like the worker of the species, which is discussed in Wang (2003) and Sarnat and Economo (2012), the alate queens of P. mandibularis vary substantially in size, shape, color and sculpture across the archipelago. The Viti Levu specimens are marked by sparse foveae, a median clypeal tooth that is smaller than the lateral teeth but still distinct, and tend towards the redder end of the color spectrum. The Vanua Levu, Koro and Lakeba specimens are moderately foveolate with a smaller and more blunted median clypeal tooth.

Comments. A puzzling taxonomic situation is presented by two alate queens from Gau occupying the extreme ends of the sculpture spectrum. Specimen CASENT0181910 lacks any distinct foveae on the head and mesosoma and is the least sculptured of the examined queens. Specimen CASENT0194557 is both exceptionally large (HW = 1.01 mm) and the mostly strongly sculptured of all examined Fijian Pristomyrmex queens, with well-defined foveae covering the head. The abundant pilosity on the head and mesosoma can be perhaps be explained by the greater number of piligerous foveae, but the length of the hairs is distinctly shorter than all other alate queens, including the aforementioned CASENT0181910 from Gau. Specimen CASENT0194557 also has shorter antennal scapes relative to its head width than any other examined alate queens of P. mandibularis or P. tsujii. The combination of gross morphological differences, morphometric disparity and sympatry of the two alate queens from Gau suggests that CASENT0194557 be assigned to a different species. We are reluctant however to describe a new species based on a single queen specimen. The aberrant measurements of CASENT0194557 are therefore reported separately from those collated from all other P. mandibularis alate queens.