Vollenhovia yambaru

Known from native forests in the northern part of the Okinawa Island.

Identification
Terayama (1999) - Total length of workers around 2.5 mm. Body color yellowish brown to reddish brown. No sculpturing on a median strip of the promesonotal dorsum, which is smooth and shining. Dorsal profile of postpetiole slightly concave posteriorly. Subpetiolar process relatively small. Queens known from ergatoid only.

I am unable to distinguish workers of this species from those of Vollenhovia okinawana. However, I treat this as a separate species because all of its known queens are wingless ergatoids, while those of okinawana are winged. Also similar to Vollenhovia benzai from Kyushu, the Tokara and the Amami Isls. However, it is distinguished from the latter by the shape of the postpetiole which is highest at posterior 1/3 and concave posterodorsal margin in the worker (highest at midlength and convex posterodorsal margin in benzai).

Distribution
Only known from Okinawa.

Distribution based on Regional Taxon Lists
Palaearctic Region: Japan.

Nomenclature

 *  yambaru. Vollenhovia yambaru Terayama, 1999e: 110, figs. 1, 2 (w.q.) JAPAN.

Worker
Holotype: HL 0.53 mm; HW 0.45 mm; SL 0.31 mm; CI 85; SI 69; WL 0.60 mm; PW 0.35 mm; PL 0.25 mm; PH 0.24 mm; DPW 0.15 mm; TL 2.1 mm. Head longer than wide, with subparallel sides and weakly concave posterior margin in full face view. Mandible with 7 teeth: basalmost tooth minute. Clypeal carinae subparallel. Antenna with 12 segments; scape 0.58 times head length. Eye 0.18 mm in maximum diameter. Dorsum of promesonotum almost straight in profile; metanotal groove not incised dorsally; posterodorsal corner of propodeum bluntly angulate, without tooth in profile. Petiole as long as high, with convex dorsal outline in profile; anterodorsal and posterodorsal corners not forming an angle. Subpetiolar process low and small: its thin lamellar wall ca. 0.04 mm in height. Postpetiole slightly longer than high, highest at posterior 1/3 in profile; posterodorsal margin concave. Head shagreened with relatively large coarse punctures; space between punctures less than 0.5 times their own diameters; dorsum of mesosoma punctated with unsculptured longitudinal band medially; mesosoma, propodeum and petiole reticulate; sculpture on petiole weaker than that on propodeum; postpetiole smooth in most part; gaster and legs smooth and subopaque. Color reddish brown; mandible, antenna, and legs yellowish brown; frons without dark brown spot.

Queen
Ergatoid: HL 0.60 mm; HW 0.53 mm; SL 0.34 mm; CI 88; SI 64; WL 0.75 mm; PL 0.25 mm; PH 0.28 mm; DPW 0.18 mm; TL 2.6 mm. Head longer than wide, with slightly concave posterior margin in full face view; mandible with 7 teeth; antennal scape not reaching posterior margin of head; eye 0.14 mm in maximum diameter; ocelli relatively small, forming a right triangle. Mesosoma with straight posterior margin in profile; in dorsal view 0.43 mm in maximum width; tegra absent; scutum relatively small, axilla and scutellum unrecognizable; posterodorsal corner bluntly angulated, without tooth; dorsum of pro- and mesonotum coarsely punctated, with smooth interspaces; mesonotum with an unsculptured longitudinal band medially. Petiole higher than long, with convex dorsal outline in ‘profile. Subpetiolar process low and small. Postpetiole highest at posterior 1/3, with concave posterodorsal margin in profile. Color reddish brown; antenna and legs yellowish brown; ocellar triangular area dark brown; frons without large brown spot.

Type Material
Holotype. Worker, Fuku-gawa, Okinawa-jima, Okinawa Pref., 4. XII. 1990, K. YAMAUCHI leg. Paratypes. 4 workers, 1 queen, same data as holotype; 1 worker, 1 queen, same locality, 31. XII. 1985, K. YAMAUCHI leg.; 2 workers, 1 queen, same locality, 30. XII. 1990, K. YAMAUCHI leg.; 6 workers, 9 males, 1 queen, Terukubi-yama, Okinawa-jima, Okinawa Pref., 22. XII. 1991, K. YAMAUCHI leg.; 2 workers, 5 queens, Chibana, Okinawa-jima, Okinawa Pref., 21. HT. 1983, H. TAKAMINE leg.

Determination Clarifications
Vollenhovia sp. 7: Terayama and Yamauchi, 1992, In Myrmecol. Soc. JAPAN (ed.), A guide for the identification of Japanese ants (III): 50.