Tetramorium pacificum Mayr, 1870

Yamane 1, Seiki, Hosoishi 2, Shingo & Ito 3, Fuminori, 2022, Japanese Tetramorium queens: identification key and species diagnoses (Hymenoptera, Formicidae, Myrmicinae), ZooKeys 1084, pp. 43-64 : 43

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Tetramorium pacificum Mayr, 1870


Tetramorium pacificum Mayr, 1870

Figs 1a View Figure 1 , 2e View Figure 2 , 4e View Figure 4 , 5e View Figure 5

Queen diagnosis.

Measurements (n = 3; material from Southeast Asia): TBL 3.5-3.8 (3.6), HL 0.81-0.86 (0.84), HW 0.70-0.74 (0.73), SL 0.53-0.55 (0.54), EL 0.21-0.23 (0.22), EW 0.16-0.18 (0.17), PtW 0.28-0.30 (0.29), PptW 0.35-0.37 (0.36), CI 86.0-88.1 (86.8), SI 71.6-75.7 (73.9), ELI 24.4-28.4 (26.7). Body brown to dark reddish or blackish-brown. Head in full-face view longer than broad, with almost parallel lateral margins. Frons sparsely longitudinally rugose with interspaces superficially sculptured and often shiny; other portions of head puncto-reticulate; antennal scrobe densely but weakly sculptured and rather shiny. Clypeus with three parallel longitudinal carinae; its anterior margin medially impressed but more weakly than in T. bicarinatum and T. nipponense . Mandible very superficially sculptured or almost smooth and shiny. Pronotal dorsum puncto-reticulate; mesonotum with parallel longitudinal rugae that are often wavy or irregular; dorsum and lateral face of propodeum puncto-reticulate or irregularly coarsely sculptured; remaining portions of mesosoma mainly striate to rugose but lower portion of mesopleuron generally smoother and shiny. Petiole in profile long; its node longer than high, with anterior slope gentle and not clearly separable from dorsum and steep posterior slope; petiole and postpetiole both dorsally and laterally distinctly sculptured and mat. Basal 1/3 or more of gastral tergite 1 covered with distinct longitudinal striae. Antennal scape and mid- and hind-tibiae without erect hairs.

Caste difference.

Worker measurements (n = 7; 3 specimens intercepted at Kure Port, Japan and 4 from Southeast Asia): TBL 2.9-3.6 (3.3), HL 0.83-0.95 (0.88), HW 0.70-0.81 (0.75), SL 0.53-0.64 (0.60), EL 0.16-0.20 (0.19), EW 0.13-0.14 (0.13), PtW 0.24-0.29 (0.27), PptW 0.29-0.37 (0.33), CI 83.3-87.9 (85.5), SI 75.7-82.9 (80.0), ELI 19.3-22.7 (21.3). Worker very similar to the queen, but with the following characteristics that are different from those of the latter. Body slightly, but constantly larger than in the queen in terms of HL, HL and SL, but eye size smaller than in the latter with ELI 21.3 (worker) vs. 26.7 (queen). Distance between anterior eye margin and mandibular base distinctly longer than major diameter of eye; in the queen, the distance as long as major diameter of eye. Entire dorsum of mesosoma coarsely puncto-reticulate; in the queen mesonotum longitudinally rugose. Mesopleuron entirely with dense minute punctures; in the queen, lower portion of mesopleuron rather smooth and sculpture in upper portion weak.

Specimens examined.

No Japanese specimen available. A dealate queen collected in Upper Thompson Nature Park, Singapore on 9.xii.2017 by Sk. Yamane was used for photos (Figs 2e View Figure 2 , 4e View Figure 4 , 5e View Figure 5 ) .


in Japan. Not established in Japan.


Tetramorium pacificum belongs to the T. bicarinatum group, in which the anterior margin of the clypeus is notched or impressed at the middle ( Bolton 1977). Amongst the species found in Japan, this species is easily distinguished from the others by having a near-smooth mandible and the anterior and dorsal faces of the petiole confluent with a smooth curve. Workers were found in a container at Kure Port, Hyogo-ken, Honshu, transported by a ferry from Zhongshan, China via Hiroshima Port. Up to now, any established population has not yet been confirmed in Japan.