Acropyga yaeyamensis

It has been found in leaf litter and at fairly high elevations (up to 1380 m), but otherwise nothing is known of its natural history.

Identification
Lapolla (2004) - Worker: 10-11 segmented antennae; mandible with 4 teeth; HW: < 0.425 mm. Queen: unknown. Male: 12 segmented antennae; parameres short, and roughly rectangular, coming to a dorsocaudal point. Compare with Acropyga oceanica.

This species most closely resembles Acropyga oceanica in its small size and 4 toothed mandible. It can be easily separated from A. oceanica based on a higher antennal segment count (10-11 segments versus 7-8 segments), and by the fact that the torulae of A. oceanica are extremely closely set together, whereas A. yaeyamensis has torulae positions that are more typical for the genus.

Distribution based on Regional Taxon Lists
Oriental Region: Nepal. Palaearctic Region: China, Japan.

From LaPolla (2004): This species has a wide range from Okinawa Island west to Nepal.

Castes
Queens have yet to be collected.

Nomenclature

 *  yaeyamensis. Acropyga (Rhizomyrma) yaeyamensis Terayama & Hashimoto, 1996: 5, figs. 13-15 (w.) JAPAN. Senior synonym of guangxiensis, yunnanensis: LaPolla, 2004a: 74. See also: Terayama, Fellowes & Zhou, 2002: 26.
 * guangxiensis. Acropyga (Rhizomyrma) guangxiensis Terayama, Fellowes & Zhou, 2002: 23, figs. 4-6 (w.) CHINA. Junior synonym of yaeyamensis: LaPolla, 2004a: 74.
 * yunnanensis. Acropyga (Rhizomyrma) yunnanensis Terayama, Fellowes & Zhou, 2002: 27, figs. 20-26 (w.m.) CHINA. Junior synonym of yaeyamensis: LaPolla, 2004a: 74.

LaPolla (2004) - The synonyms, A. guangxiensis and A. yunnanensis, based on worker morphology are indistinguishable from each other and A. yaeyamensis. Terayama et al. (2002) discussed differences in mesosomal characters and number of ommattidia to separate the supposed species, but those characters are unreliable. The differences in mesosomal structure, the metanotal area being either distinct or indistinct, could easily be intraspecific variation, as is seen in many other Acropyga species. Terayama et al. (2002) state differences from 1 ommattidium to 4 ommattidia to separate A. guangxiensis and A. yunnanensis repectively, but such small differences in ommatidia number to separate species is unreliable since the extent of variation in that character remains unknown. Nonetheless, it is important to note that the male described in this study as A. yaeyamensis is geographically distant (Nepal) from the type locality. As males of this species are collected from across its range they should be examined with associated worker specimens to make certain there is not in reality more than one species present in a group of morphologically very similar workers. Although I have not examined the male described for A. yunnanensis, the figure provided matches the specimen used in this study for A. yaeyamensis very closely. Until males can be associated with workers and used to distinguish separate species I feel it unwarranted at this time to recognize more than one species.

Worker
LaPolla (2004) - Head: yellow; head longer than broad; posterior margin entire to slightly concave medially; covered in a thick layer of appressed hairs; 10-11 segmented, incrassate antennae; scape fails to reach posterior margin by about length of pedicel; clypeus narrow, with scattered erect hairs; mandible with 4 approximately similarly sized teeth; 4th tooth sometimes separated from others by a short diastema; slight gap between inner mandibular margin and anterior clypeal margin. Mesosoma: yellow; in lateral view, pronotum with short anterior shelf before rising toward mesonotum; with sparse covering of appressed to erect hairs; mesonotum rounded dorsally, with dense layer of appressed hairs to scattered erect hairs; mesonotum often higher than propodeum; metanotal area often distinct; propodeum rounded dorsally, with layer of appressed hairs; declivity steep. Gaster: petiole thick and erect reaching height propodeal spiracle; gaster yellow, covered in thick layer of appressed hairs, with scattered erect hairs throughout.

Measurements (n=3): TL: 1.28-1.38; HW: 0.378-0.419; HL: 0.43-0.454; SL: 0.244- 0.294; ML: 0.344-0.41; GL: 0.498-0.535; CI: 87.91-92.76; SI: 64.55-71.71.

Male
LaPolla (2004) - Head: brownish-yellow, darker toward apex around 3 prominent ocelli; head longer than broad; covered in a thick layer of appressed hairs; 12 segmented, incrassate antennae; scape fails to reach posterior margin by about half length of the pedicel; clypeus narrow, slightly convex medially, with scattered erect hairs; mandible with 2 teeth, widely separated by a diastema; a slight gap between inner mandibular margin and anterior clypeal margin. Mesosoma: unfortunately the mesosoma of the single known male specimen was too badly distorted to be described properly. Gaster: brownish-yellow; covered in a thick layer of appressed hairs with scattered erect hairs throughout. Genitalia: in lateral view parameres short, roughly rectangular, dorsocaudally coming to a point; cuspi bent toward digiti, with short, peg-like teeth at apices; digiti about about as long as cuspi, apically anvil-shaped; digiti with short, peg-like teeth where they meet cuspi.

Type Material
LaPolla (2004):

Acropyga (Rhizomyrma) yaeyamensis Terayama and Hashimoto, 1996: 5 (w.). Holotype worker, JAPAN: Urauchi, Iriomote-jima, Yaeyama Is., Okinawa Pref. (M. Terayama) [examined]. Terayama et al., 2002: 26, description and key.

Acropyga (Rhizomyrma) guangxiensis Terayama, Fellowes, and Zhou, 2002: 23 (w.). Holotype worker, CHINA: Guanxi, Huaping (J.R. Fellowes) (ICKH) [not examined]. NEW SYNONYM.

Acropyga (Rhizomyrma) yunnanensis Terayama, Fellowes, and Zhou, 2002: 27 (m.). Holotype male, CHINA: Yunnan, Xishuangbanna, Nangong-shan (Z. Xu) (ISYC) [not examined]. NEW SYNONYM.