Probolomyrmex okinawensis

According to Mr. Mizukami (pers. comm.), the colony of this species collected by him was found under a stone on the floor of evergreen forest (Terayama and Ogata 1988). It is rare, and known only from Okinawa, Japan.

Identification
Eguchi et al. (2006) - This species is similar to Probolomyrmex maryatiae and Probolomyrmex vieti, but distinguished from the latter two by the posteroventral portion of subpetiolar process forming only an obtuse angle in the worker and queen.

Distribution
Known only from Okinawa-jima (C. Ryukyus).

Distribution based on Regional Taxon Lists
Palaearctic Region: Japan.

Nomenclature

 *  okinawensis. Probolomyrmex okinawensis Terayama & Ogata, 1988: 591, figs. 1-5 (w.q.) JAPAN.

Worker
HL 0.50-0.53 mm; HW 0.33-0.35 mm; SL 0.30-0.33 mm; CI65-68; SI92-93; WLO.65--O.70mm; PWO.25mm; PNWO.l5mm; PNI60; petiolar H 0.22-0.23 mm; PNL 0.20-0.21 mm; LPI 89-94; TL 1.9-2.0 mm. (Three individuals were measured.)

Smaller species. Head with convex sides and shallowly concave occipital border, posterolateral corners rounded. Mandibles small, covered by frontoclypeal projection, elongate triangular, each with a larger acute apical tooth followed by a series offour small denticles. Labio-maxillary complex not dissected. Antennae 12-segmented; scapes short, not reaching the middle of head length; 2nd antennal segment longer than broad, 1.5 X as long as broad; 3rd to l1th each broader than long; apical segment 1.5 X as long as broad, slightly longer than three preceding segments together. Eyes absent.

General form of trunk and petiole as in Fig. Dorsal outline of trunk straight; posterolateral corners of propodeum pronounced, forming blunt angles; posterior declivity of propodeum strongly concave in dorsal view; dorsal sutures of trunk absent. Legs long; middle and hind tibiae each with a distinct pectinate spur, but lacking smaller simple spur. Petiole including subpetiolar process higher than long; anterior portion bending to form convex anterior face and arched dorsal face; posterior face almost vertical and marginate laterally; posterodorsal margin transversely straight in dorsal view. Subpetiolar process developed; anteroventral portion distinctly projected, with rounded corner; posteroventral portion forming obtuse angle without acute tooth. Anterior margin of first gastric segment rounded in dorsal view; second gastric tergum excluding acrotergite about 0.8 X as long as first one; sting well developed.

Head, trunk, petiole and gaster shagreened, with overlying punctures; antennal scapes and legs slightly less so. Pilosity reduced. Color reddish brown.

Queen
(dealated). HL 0.54-0.56 mm; HW 0.36-0.38 mm; SL 0.32 mm; CI 66.7-67.9; SI84.2-88.9; WL 0.70-0.72 mm; MW 0.26 mm; PNW 0.16-0.18 mm; petiolar H 0.28 mm; PNL 0.22 mm; LPI78.6; TL 1.7-1.8 mm. (Two individuals were measured.)

Posterior margin of head straight. Mandibles with one large apical, one subapical and 3 minute teeth. Labio-maxillary complex not dissected. Antennal scapes exceeding beyond the level of eyes, but not reaching anterior ocellus.

Eyes large but not convex, situated anterior to the middle of sides of head; its greatest diameter ca. 0.08 mm in length.. Ocelli distinct but less convex. General form and the remainder of head like those of worker.

Trunk large and robust. Pronotum not overhung by mesoscutum. Mesoscutum and mesoscutellum gently arched above; notauli absent, parapsidal furrows weakly developed on mesoscutum; mesoscutum long, more than twice as long as mesoscutellum; mesepisternum with oblique furrow; epimerallobe absent. Metanotum narrow but distinct, not overhung by mesoscutellum. Propodeum with rounded dorsal face and concave posterior face which bears lateral margination as in worker. Legs, petiole and gaster like those of worker but more massive. Surface sculpture, pilosity and body color as in worker.

Type Material
Eguchi et al. (2006) - Holotype: worker, Chibana, Okinawa-hontou Is. [Okinawa-jima], Ryukyus, Japan, 19/iii/1983, T. Mizutani (Faculty of Agriculture, Kyushu Univ., Japan) [examined]. Paratypes: 4 workers from the same nest as the holotype [one paratype examined (loaned from the Institute of Tropical Agriculture, Kyushu Univ.)]; 1 dealate queen and 1 worker, Nakasone, Okinawa-hontou Is., 20/xi/1975, T. Abe [not examined]; 1 dealate queen from Nakijin-joushi, Okinawa-hontou Is., 7/iii/1984, K. Onoyama [examined (loaned from the Institute of Tropical Agriculture, Kyushu Univ.)].

References based on Global Ant Biodiversity Informatics

 * CSIRO Collection
 * Eguchi K.; Yoshimura M.; Yamane S. 2006. The Oriental species of the ant genus Probolomyrmex (Insecta: Hymenoptera: Formicidae: Proceratiinae). Zootaxa 1376: 1-35.
 * Terayama M. 1992. Structure of ant communities in East Asia. A. Regional differences and species richness. Bulletin of the Bio-geographical Society of Japan 47: 1-31.
 * Terayama M., Ogata K. 1988. Two new species of the ant genus Probolomyrmex (Hymenoptera, Formicidae) from Japan. Kontyû 56: 590-594
 * Terayama M., S. Kubota, and K. Eguchi. 2014. Encyclopedia of Japanese ants. Asakura Shoten: Tokyo, 278 pp.
 * Terayama M., and K. Ogata. 1988. Two new species of the ant genus Probolomyrmex (Hymenoptera, Formicidae) from Japan. Kontyu, Tokyo 56(3): 590-594.
 * Terayama, Mamoru and Kazuo Ogata. 1988. Two New Species of the Ant Genus Probolomyrmex from Japan. Kontyu, Tokyo. 56(3):590-594.
 * Yamane S., S. Ikudome, and M. Terayama. 1999. Identification guide to the Aculeata of the Nansei Islands, Japan. Sapporo: Hokkaido University Press, xii + 831 pp. pp, 138-317.
 * Yamane S.; Ikudome, S.; Terayama, M. 1999. Identification guide to the Aculeata of the Nansei Islands, Japan. Sapporo: Hokkaido University Press, xii + 831 pp. pp138-317.