Strumigenys benten

The species nests at the margins of broadleaf forests and adjacent open land where it nests in the soil or under stones and sampled in Berlese funnel forest-litter samples. A colony collection (Takatsuki, Osaka Prefecture, Japan) was found under a concrete stone among thinly spaced trees on the precints of a temple. It included more than 150 workers (Ogata & Onoyama, 1998). It is most common in the southern part of Honshu south to Kyushu (Japanese Ant Image Database).

Identification
Bolton (2000) - A member of the Strumigenys leptothrix-group. This species is very closely related to Strumigenys alecto but has the differences tabulated below. The two may eventually prove to be extreme variants of a single species (Ogata & Onoyama, 1998).  Strumigenys formosimonticola may also be involved in the variation as Touyama (1998) has documented some interesting pilosity variants that he includes under benten. Until more material is available I regard the following features as being diagnostic of two separate but sibling species, because the distribution and density of specialised pilosity is usually fairly stable in Pyramica species.

S. alecto: With head in profile the dorsum with short erect simple hairs at, in front of and behind the highest point of the vertex. With the head in occipital view 20 or more short erect hairs visible on dorsum. Dorsal (outer) surfaces of middle and hind tibiae with numerous short straight projecting simple suberect hairs. Pronotal dorsum with short erect hairs present anteriorly other than those at the humeri. Pronotal dorsum finely reticulate-punctate.

S. benten: With head in profile the dorsum with short erect hairs only behind highest point of the vertex. With the head in occipital view no more than 8-10 short erect hairs visible on dorsum. Dorsal (outer) surfaces of middle and hind tibiae with apically directed appressed hairs only. Pronotal dorsum without erect hairs except at the humeri. Pronotal dorsum not reticulate-punctate.

Japan
The species is similar to Strumigenys leptothrix, but distinguished by its pilosity: the hairs on the head of S. benten are shorter, more sparse and somewhat clavate, and those on the anterior portion, in particular, are depressed. It should be noted that the pilosity of S. benten is variable. Samples from the Kanto District tend to have shorter, more sparse hairs on the head than those from Kyushu, where the hairs are longer and more dense. The first gastral segment sometimes lacks hairs. (Japanese Ant Image Database)

Touyama (1998) reported that hairs on the vertex may be often lacking in S. benten. Bolton (2000) described the hairless form as a separate new species named Strumigenys alecto. We believe the separate specific status of "alect" from S. benten to be questionable, requiring further study. For this reason we do not recognize S. alecto at this time.

Distribution based on Regional Taxon Lists
Oriental Region: Taiwan. Palaearctic Region: Japan.

Nomenclature

 *  benten. Smithistruma benten Terayama, Lin & Wu, 1996: 329, figs. 1-5, 20 (w.q.) TAIWAN. Combination in Pyramica: Bolton, 1999: 1673; in Strumigenys: Baroni Urbani & De Andrade, 2007: 116. See also: Bolton, 2000: 431.

Worker
Bolton (2000) - TL 2.1- 2.6, HL 0.60-0.65, HW 0.44-0.50, CI 71-82, ML 0.13-0.17, MI 13-15 [measurement in Terayama, Lin & Wu (1996: 330) of MI 21-28, is too high; from specimens examined and their fig. 1, MI should be as above], SL 0.26-0.32, SI 59, PW 0.26-0.33, AL 0.65-0.72. Terayama, Lin, & Wu, (1996: 330) give a total dental count of 12 for benten but a specimen with mandibles ajar that I have examined had 14.]

Type Material
Bolton (2000) - Holotype worker and paratype workers and queens, TAIWAN: Nantou Hsien, Lienhuachih, 12.xi.1992 (C.-C. Lin). Paratype workers and queens, TAIWAN: Nantou Hsien, Taping-Meitzulin, ca 510 m., 30.vii.1988 (M. Terayama). JAPAN: Okinawa Pref., Ryukyu Is, Iriomote-jima I., 30.iii.1991 (M. Terayama); Mie Pref., Yokkaichi-shi, 21.iv.1987 (A. Amagasu); Mie Pref., Komono-machi, xii.1989 (M. Terayama); Komaba, Meguro-ku, Tokyo, 30.vi.1986 (M. Terayama); Tokyo, Nakano-ku, 19.viii.1980 (S. Kubota) [NSMT paratypes examined].

References based on Global Ant Biodiversity Informatics

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