Proceratium itoi (Forel, 1918)

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 itoi (Forel, 1918) Figs 1B, 3B, 3D, 5A, 10, 11, 24

Sysphincta itoi Forel, 1918: 717 (w.), Japan

Proceratium itoi - Brown 1958: 247 (see also Baroni Urbani and de Andrade 2003: 267, Onoyama and Yoshimura 2002: 32)

Proceratium itoi - Ogata 1987: 107 (m.), Japan

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

Type material.

Syntypes. Three pinned workers from JAPAN, Tokyo, leg. Ito (CASENT0907205, in MHNG) [images examined].

Non-type material examined.

JAPAN, Fukuoka, Mt. Tachibana, 25-VII-1984, leg. S. Nomura (OKENT016137; OKENT016138; OKENT016139; OKENT016141; OKENT016142, all in OIST).

Virtual dataset.

Volumetric raw data (in DICOM format), 3D rotation video (in.mp4 format, see Suppl. material 4: Video 2), still images of surface volume rendering, and 3D surface (in PLY format) of a non-type specimen (OKENT0016142) 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/6txMM).

Diagnosis.

Proceratium itoi differs from the other members of the P. itoi clade by the following character combination: medium-sized species (TL 3.46-3.82); sides of head very weakly convex, almost straight, broadest at level of eyes and gently narrowing anteriorly and posteriorly, vertex weakly convex, almost straight; frontal carinae well developed, with large lamellae that extend laterally above the antennal insertions; frontal furrow inconspicuous; posterodorsal corners of propodeum rounded, propodeal declivity superficially punctured (more so dorsally) but largely shiny; posterior face of petiolar node in profile steeper as anterior face; petiole almost as broad as long (DPeI 86-93), apex of petiolar node broader than long in dorsal view; subpetiolar process developed and triangular (but may be small); in addition to dense pubescence abundant erect hairs present on scapes and dorsal surface of body, longest of those hairs shorter than maximum dorsoventral diameter of metafemur.

Distribution and ecology.

This species is widely distributed, occurring from Japan (except Hokkaido) and South Korea to Vietnam. It has been recorded from Taiwan and the Chinese provinces Zhejiang and Hunan. Thus, we expect that it will be collected from the geographically intermediate provinces in the future. No direct biological observations from China are available, but the Japanese populations are comparatively well studied ( Onoyama and Yoshimura 2002). Nests are found in the soil or rotting wood of various deciduous or evergreen forest types and workers forage hypogeic or in leaf litter. Mature colonies have 100-200 workers and densities can reach 0.3 colonies per m² ( Masuko 2010). Larval hemolymph feeding has been observed ( Masuko 1986).

Taxonomic notes.

Proceratium itoi is a typical member of its clade of intermediate size (WL 0.96-1.04) and is similar to most other species in body proportions and indices. Proceratium itoi can be separated from P. williamsi and P. zhaoi by the presence of erect hairs on the dorsal body surface (absent in P. williamsi and P. zhaoi ); from P. longmenense by the presence of erect hairs on the scape (absent in P. longmenense ) and by the frontal carinae separated at their anteriormost level (touching each other at their anteriormost level in P. longmenense ). In P. itoi the posterodorsal corners of propodeum are rounded and this character distinguishes this species from P. bruelheidei and P. kepingmai (posterodorsal corners of the propodeum angular), which are also larger species (WL 1.03-1.10 and 1.14-1.24). The rounded posterodorsal corners of propodeum are shared between P. malesianum and P. itoi , but P. malesianum is a smaller species (WL 0.71-0.90) with a broadly rounded vertex (weakly convex, almost straight in P. itoi ) and a broadly rounded petiolar node in profile (posterior face of petiolar node in profile steeper than anterior face in P. itoi ).