Tetramorium tsushimae Emery, 1925

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

Tetramorium tsushimae Emery, 1925

Figs 1e , 3c , 4i , 6c

Queen diagnosis.

Measurements (n = 5): TBL 5.9-7.0 (6.4), HL 1.14-1.18 (1.17), HW 1.24-1.31 (1.27), SL 0.79-0.90 (0.84), EL 0.33-0.35 (0.34), EW 0.25-0.28 (0.26), PtW 0.45-0.50 (0.47), PptW 0.68-0.77 (0.74), CI 108.5-110.2 (109.1), SI 62.3-70.3 (66.2), ELI 28.0-29.7 (28.9). Body dark reddish-brown to blackish-brown. Head distinctly broader than long (CI ca. 109); entire head densely and regularly striate, with reticulate area restricted. Frontal carina weak and antennal scrobe barely recognisable. Clypeus with around ten longitudinal carinae; anterior margin entire. Mesosoma extensively striate to rugose, with smooth areas in anteromedian portion and area along parapsidal line of mesoscutum and longitudinal median zone of mesoscutellum; sculpture on pronotum, metapleuron and lateral face of propodeum coarser than in other areas; propodeum with striation longitudinal and irregular on dorsum and dense and transverse on declivity; interspaces minutely punctate. Metapleural lobe low, generally with round apex. Petiole in dorsal view dorsum very short (often indistinct), 1/6 to 1/5 as long as broad; postpetiole very broad, 1.57 × as broad as petiole. Gastral tergite 1 entirely smooth, but sometimes with very superficial sculpture near base. All erect hairs simple and more or less tapering apicad. Antennal scape and mid- and hind-tibia without erect hairs.

Caste difference.

Worker measurements (n = 5): TBL 2.48-2.88 (2.71), HL 0.70-0.88 (0.77), HW 0.63-0.84 (0.71), SL 0.53-0.63 (0.57), EL 0.13-0.17 (0.15), EW 0.10-0.12 (0.11), PtW 0.18-0.28 (0.23), PptW 0.25-0.35 (0.29), CI 88.7-95.5 (92.1), SI 75.0-87.3 (81.1), ELI 18.1-18.3 (19.2). Worker very similar to the queen in colouration, structure, sculpture and pilosity, but differing in the following aspects: body much smaller; head longer than broad (CI ca. 92 vs. ca. 109 in the queen.); striation on mesonotum sparser and more irregular than in the queen; petiole more globular than in the queen, with rather distinct dorsum, which is in dorsal view only slightly broader than long; both petiole and postpetiole dorsally with smooth areas; in the queen almost entirely sculptured.

Specimens examined.

Honshu: 1q (dealate), Mihagi-dai, Hagi-shi, Yamaguchi-ken, 12.x.2013, nest under stone, Sk. Yamane leg. (JP13-SKY-27); 1q (dealate), Niino-hama, Heki, Nagato-shi, Yamaguchi-ken, 12.x.2013, nest under stone, Sk. Yamane leg. (JP13-SKY-28). Kyushu: 3q (dealate), Nokonoshima, Fukuoka-shi, Fukuoka-ken, 3.viii.2020, under stone, S. Hosoishi (SH20-Jpn-01) (Figs 3c , 4i , 6c ); 2q (winged), Haruyama, Matsumoto-chô, Kagoshima-ken, 15.vi.2000, nest in soil, Sk. Yamane leg. (KG00-SKY-02).

Distribution in Japan.

Hokkaido, Honshu, Shikoku, Kyushu, Ôsumi Islands, Tokara Islands. The southern limit lies in Suwanose-jima of the Tokara Islands ( Yamane and Fukumoto 2017).

Remarks.

Tetramorium tsushimae belongs to the T. caespitum species group. In the queen caste this species is easily distinguished from other Japanese congeners by the large and blackish-brown body, broad head, ill-defined antennal scrobe, presence of smooth areas on the mesonotum and very short petiole.

Figures

Figure 1. Some important characters used in the key to species a-e petiole in profile view a T. pacificum b T. lanuginosum c T. bicarinatum d T. smithi e T. tsushimae f-h anterior half of first gastral tergite f T. bicarinatum g T. simillimum h T. lanuginosum i-k antennal scape showing pilosity on its anterior margin l-n left hindtibia i, l T. cf. kraepelini j, m T. nipponense k, n T. simillimum o, p configuration of ocelli o T. tanakai p T. cf. kraepelini.

Figure 3. Japanese Tetramorium queens: habitus in profile a T. smithi (Hirarahigashi, Miyako-jima, Okinawa-ken) b T. tanakai (Mandabaru, Yonaguni-jima, Okinawa-ken) c T. tsushimae (Nokono-shima, Fukuoka-shi). (Same specimens were used for ' head in full-face view' and ' habitus in dorsal view').

Figure 4. Japanese Tetramorium queens: head in full-face view a T. bicarinatum b T. cf. kraepelini c T. lanuginosum d T. nipponense e T. pacificum f T. simillimum g T. smithi h T. tanakai i T. tsushimae.

Figure 6. Japanese Tetramorium queens: habitus in dorsal view a T. smithi b T. tanakai c T. tsushimae.