Tetramorium simillimum (F. Smith, 1851)

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 simillimum (F. Smith, 1851)

Figs 1g, k, n , 2f , 4f , 5f

Queen diagnosis.

Measurements (n = 4): TBL 2.3-2.6 (2.5), HL 0.60-0.63 (0.62), HW 0.53-0.58 (0.56), SL 0.39-0.43 (0.41), EL 0.17-0.18 (0.18), EW 0.13 (0.13), PtW 0.20-0.23 (0.22), PptW 0.25-0.28 (0.27). Body yellowish-brown, with darker gaster and light brown to yellow legs. Dorsum of head with dense and longitudinal striae that are regular and parallel; interspaces microsculptured and mat. Clypeus with strong median carina; other longitudinal carinae weak, indistinct; anterior margin entire. Distance between anterior eye margin and mandibular base distinctly shorter than major diameter of eye. Dorsum of mesosoma entirely sculptured; pronotum reticulate, with anterolateral corner angulate; entire mesonotum densely with longitudinal striae; in profile lateral face of mesosoma entirely sculptured; upper portion of mesopleuron rugose and lower portion densely punctate (sometimes punctation weak). Propodeum with longitudinally puncto-striate dorsum and transversely puncto-striate declivity, entirely mat, without transverse carinae between propodeal spines; propodeal spine short, apically blunt, only slightly longer than metapleural lobe. Petiolar node anteriorly sharply truncate; petiole and postpetiole entirely sculptured; ventre of petiolar peduncle superficially sculptured and weakly shiny; nodes of both petiole and postpetiole coarsely punctured. Gastral tergite 1 in basal 1/3 densely and minutely punctate or coriaceous, mat or weakly shiny. Antennal scape and mid- and hind-tibiae without erect hairs. Erect body hairs not tapering apicad, apically often truncate or blunt.

Caste difference.

Worker measurements (n = 5): TBL 1.8-2.1 (1.9), HL 0.53-0.59 (0.56), HW 0.45-0.53 (0.49), SL 0.33-0.39 (0.36), EL 0.11-0.13 (0.12), EW 0.08-0.09 (0.08), PtW 0.16-0.18 (0.17), PptW 0.19-0.23 (0.21), CI 83.3-89.8 (87.4), SI 71.7-77.6 (74.6), ELI 20.0-22.6 (21.1). Worker very similar to the queen, but with the following differences. Body smaller than in the queen. Distance between anterior eye margin and mandibular base as long as or slightly longer than major diameter of eye; in the queen, the distance much shorter than major eye diameter. Mesonotum coarsely rugoso-reticulate, rugae wavy and irregular; in the queen striae fine and regular. Gastral tergite 1 entirely smooth and shiny; in the queen basal area of the tergite micropunctured and mat (sometimes microsculpture very faint and cuticle weakly shiny). Apical truncation of erect hairs on head and mesosoma more distinct; in the queen, erect hairs often not typically truncate.

Specimens examined.

C. Ryukyus: 1q, (dealate), Nagahama-chô, Naze, Amami-ôshima, 17.vi.2017, in dead twig on ground, F. Ito leg.; 1q (dealate), same loc., date and nesting site, F. Ito (FI17-102); 2q (dealate), Yoron-jima, 28.v-2.vi.1999 (Figs 2f , 4f , 5f ).

Distribution

in Japan. Nansei Islands, Ogasawara Islands, Volcano Island. Northern limit lies in Kodakara-jima of the Tokara Islands ( Yamane and Fukumoto 2017).

Remarks.

Tetramorium simillimum belongs to the T. simillimum species group ( Bolton 1977). In the queen, it is easily distinguished from other Japanese congeners by the following character conditions: i) dorsum of head with regular longitudinal striae, with interspaces densely sculptured and mat; ii) erect body hairs not sharply pointed apically; iii) petiole anteriorly truncate, with dorsal face clearly separated from anterior slope with sharp angle; iv) basal 1/3 of gastral tergite 1 micropunctate or coriaceous and mat (sometimes weakly shiny). This species is a famous tramp of African origin ( Bolton 1977; Yoshimura 2020).

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 2. Japanese Tetramorium queens: habitus in profile view a T. bicarinatum (Nagashima, Kagoshima-ken, Kyushu) b T. cf. kraepelini (Itoman, Okinawa-jima, Okinawa-ken) c T. lanuginosum (Komi, Iriomote-jima, Okinawa-ken) d T. nipponense (Umi-jinja, Shikano-shima, Fukuoka-shi) e T. pacificum (Upper Thompson Nature Park, Singapore) f T. simillimum (Yoron-jima, Amami Is., Kagoshima-ken). (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 5. Japanese Tetramorium queens: habitus in dorsal view a T. bicarinatum b T. cf. kraepelini c T. lanuginosum d T. nipponense e T. pacificum f T. simillimum.