Proceratium japonicum Santschi, 1937

Staab, Michael, Garcia, Francisco Hita, Liu, Cong, Xu, Zheng-Hui & Economo, Evan P., 2018, Systematics of the ant genus Proceratium Roger (Hymenoptera, Formicidae, Proceratiinae) in China - with descriptions of three new species based on micro-CT enhanced next-generation-morphology, ZooKeys 770, pp. 137-192 : 137

Proceratium japonicum Santschi, 1937 Figs 1A, 2B, 18, 19, 24

Proceratium japonicum Santschi, 1937: 362 (w.), Japan (see also Baroni Urbani and de Andrade 2003: 368, Onoyama and Yoshimura 2002: 38)

Proceratium formosicola Terayama, 1985: 406 (w.q.), Taiwan (junior synonym, see Onoyama 1991: 695)

Proceratium japonicum - Onoyama and Yoshimura 2002: 35 (q.m.), Japan

Type material.

Of P. japonicum : Syntypes. Three pinned workers from JAPAN, Honshu, Oshima, Iya, Honshiu, 10.VI.28, leg. K. Sato (CASENT0915312, in NHMB) [images examined].

Of P. formosicola : Holotype. TAIWAN, Nantou Hsien, Lushan, ca. 100 m asl, 15-VIII.1980, leg. M. Terayama. (in NIAES) [not examined].

Paratypes. Two pinned workers and one queen with same data as holotype; one pinned worker from TAIWAN, Nantou Hsien, Puli, 4-VIII.1981, leg. M. Terayama (TARI) [not examined].

Non-type material examined.

JAPAN: Okinawa, Ishigaki Island, Mt. Omoto, 1-IV-1975, leg. M. Tanaka (CASENT0281854, in BMNH); JAPAN, Okinawa, Irimote Island, Shirahama, 6-V-2000, leg. M. Yoshimura (OKENT0019995; OKENT0019996, both in OIST); JAPAN, Kanagawa, Odawara, Minazurimisaki, 27-VII-2000, leg. M. Yoshimura (CASENT0790834; OKENT0019998; OKENT0019999; OKENT0020000, all in OIST).

Virtual dataset.

Volumetric raw data (in DICOM format), 3D rotation video (in.mp4 format, see Suppl. material 8: Video 6), still images of surface volume rendering, and 3D surface (in PLY format) of a non-type specimen (CASENT0790834) in addition to montage photos illustrating head in full-face view, profile and dorsal views of the body. The data is deposited at Dryad ( Staab et al. 2018, http://dx.doi.org/10.5061/dryad.h6j0g4p) and can be freely accessed as virtual representation of the species. In addition to the data at Dryad, we also provide a freely accessible 3D surface model at Sketchfab (https://skfb.ly/6txNO).

Diagnosis.

Proceratium japonicum differs from the other east Asian members of the P. silaceum clade by the following character combination: medium-sized species (WL 0.72-1.00); sides of head convex, broadest above the level of eyes; anterior clypeal margin not protruding and slightly notched; frontal carinae well developed and widely separated, with large lamellae that extend laterally above the antennal insertions and reach posteriorly almost to the level of eyes; frontal furrow strongly developed; petiole squamiform, in profile not or only weakly narrowing dorsally, the base as or almost as broad as the apex, in dorsal view relatively narrow (DPeI <150); subpetiolar process developed, subtriangular, directing backwards; sculpture not deeply impressed, on abdominal segment III granulate and relatively regular; in addition to dense pubescence, some suberect to erect hairs present on scapes and dorsal surface of body.

Distribution and ecology.

This species is common from Japan (except Hokkaido) to Taiwan and usually collected in forests of relatively low elevation. It has also been reported from Yunnan Province in China. Thus, it is not unlikely that more records from the southern and eastern Chinese mainland will appear in the future if sampling effort is increased. No direct biological observations from China are available. In Japan, nests are typically found in deadwood in evergreen broadleaved forest ( Onoyama and Yoshimura 2002). Colony size can reach over 150 workers and larval haemolymph feeding has been observed ( Masuko 1986).

Taxonomic notes.

According to Baroni Urbani and de Andrade (2003) P. japonicum is most similar to P. numidicum Santschi, 1912, which is, however, a geographically widely separated species occurring in the eastern Mediterranean and northern Africa. We were not able to examine P. japonicum material from China. In Japan, specimens from the Ryukyu and Yaeyama islands are smaller than from the main islands ( Onoyama and Yoshimura 2002, Baroni Urbani and de Andrade 2003), explaining the relatively large variation in body size.

From P. longigaster , the only other P. silaceum clade species in China and east Asia, P. japonicum can be separated by the shape of the petiole in profile that not or only weakly narrows dorsally (clearly narrowing dorsally, broader on the base than on the apex in P. longigaster ). Also, the petiole in dorsal view is narrower in P. japonicum (DPeI <150) than in P. longigaster (DPeI ≥155). Furthermore, the frontal carinae in P. japonicum reach posteriorly almost to the level of eyes (shorter and ending well below the level of eyes in P. longigaster ). Proceratium japonicum has only relatively few suberect to erect hairs that protrude from the dense pubescence on the dorsal body; those hairs are straight (never shaggy) and do not conspicuously project from LT3 over the constriction between LT3 and LT4 (many shaggy hairs projecting in P. longigaster ); if single longer hairs are present, then they are not shaggy.