Tetramorium simillimum

Nomenclature

Species: Tetramorium simillimum (Smith, F. 1851)

Holotype: BPBM - ANTC18479 - CASENT0249091
Holotype: BPBM - ANTC18480 - CASENT0249092
Holotype: BPBM - ANTC18481 - CASENT0249093

General description

Tetramorium simillimum is a small pale colored ant. This species has a monomorphic worker caste with 12-segmented antennae, three-segmented antennal club, antennal scrobes, short antennal scapes that do not surpass the posterior margin of the head, a gradually sloped mesosoma, and small propodeal spines. Like all myrmicines, T. simillimum has two waist segments and a gaster armed with a stinger. Tetramorium simillimum is believed to be native to Africa and is now widely distributed across tropical regions. The species can achieve dense populations in disturbed habitats and is likely to adversely affect native biodiversity.

External links

Antweb | Antwiki

Diagnostic description

Diagnosis of worker among Antkey species

Worker caste monomorphic. Head shape roughly subrectangular. Antenna 12-segmented. Antennal club 3-segmented. Antennal scapes not conspicuously short; easily extended beyond eye level; do not extend beyond posterior margin of head. Antennal scrobe present but weakly impressed with the frontal carinae usually becoming indistinct at its posterior apex. Antennal insertion surrounded by a raised sharp-edged ridge. Posterior margin of head weakly concave medially. Posterolateral corners of head unarmed, without spines. Eyes medium to large (greater than 5 facets); distinctly less than half head length. Frontal lobes do not obscure face outline between mandible and eye; relatively far apart so that the posteromedian portion of the clypeus, where it projects between the frontal lobes, is much broader than one of the lobes. Anterior margin of clypeus lacking median notch. Mandibles triangular. Cephalic dorsum with short lateral rugae intersecting longer longitudinal rugae. Mesosoma with erect hairs. Pronotal spines absent. Propodeum armed with small but distinct triangular spines. Slope of mesosoma gradual. Waist 2-segmented. Petiole with a square-shaped node; pedunculate; lacking large subpetiolar process postpetiole attached to lower surface of gaster. Postpetiole not swollen; in dorsal view not distinctly broader than long or distinctly wider than petiole. Erect hairs sparsely distributed; short and thick. Specimen vary between uniformly yellowish brown to yellowish brown with a distinctly darker brown to black gaster.

Tetramorium simillimum, together with T. caldarium, look very much like Wasmannia auropunctata in general size and shape. The Tetramorium species can be separated on closer examination by the 3-segmented (versus 2-segmented) antennal club, the much shorter propodeal teeth, and the difference in petiole shape. All Tetramorium can be separated from other genera with introduced or commonly intercepted species by the raised sharp-edged ridge surrounding the antennal insertions. Tetramorium simillimum is distinguished from its fellow congeners that are introduced in the United States by the following combination of characters: (1) petiolar node square-shaped (versus evenly rounded for T. lanuginosum and T. tonganum; versus wave-shaped for T. insolens and T. pacificum); (2) erect hairs sparse, short and thick (versus moderately to very abundant, long and thin for T. bicarinatum, T. nr. caespitum, T. caldarium, T. lanuginosum, T. simillimum and T. tsushimae; versus wave-shaped for T. insolens and T. pacificum); (3) cephalic dorsum with short lateral rugae intersecting longer longitudinal rugae (versus primarily subparallel, non-intersecting longitudinal rugae for T. nr. caespitum and T. tsushimae); and (4) propodeum armed with small triangular teeth (versus long and robust spines in T. bicarinatum, T. insolens and T. pacificum). It is very difficult to separate T. caldarium from T. simillimum. The antennal scrobe of T. simillimum is more impressed, and the frontal carina remains distinct even at its posterior apex. It also appears that T. simillimum may have a more broad petiolar peduncle and node in profile, and a more flat posterior head margin, but these characters require additional analysis.

Distribution

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Videos of live ants

Tetramorium simillimum at peanut butter bait (Fiji, 2008)

Tetramorium simillimum at peanut butter bait with T. bicarinatum (Fiji, 2008)

<em>Tetramorium simillimum</em> at peanut butter bait

Tetramorium simillimum at peanut butter bait (Suva, Fiji).

Tetramorium simillimum at peanut butter bait (Suva, Fiji). Notice the uniform red color, small size, and slow and deliberate movements.

Lateral dorsal view of body, entire, adult worker. Tetramorium simillimum worker at peanut butter bait. Suva, Fiji, 1-24-2008.	Multiple views of body, entire, multiple life stages worker. Tetramorium simillimum workers and pupae in excavated nest. Suva, Fiji, 1-24-2008.
Multiple views of body, entire, adult worker. Tetramorium simillimum workers at peanut butter bait. Lautoka, Fiji, 1-27-2008. Units in mm.	Multiple views of body, entire, adult worker. Tetramorium simillimum workers at peanut butter bait. Lautoka, Fiji, 1-27-2008.
Lateral view of body, entire, adult.	Dorsal view of body, entire, adult. Scale bar is 0.5 mm long.
Anterior view of head, adult worker.	Anterior view of head, adult worker. Posterior margin of the head is generally flat, lacking a median impression. Used in Antkey to separate Tetramorium simillimum from T. caldarium. This character is based on examination of limited material.
Anterior view of antennal scrobe, adult worker. Antennal scrobe more distinct.	Anterior view of head, adult worker. Separates Tetramorium simillimum from T. caldarium, but can be difficult to observe. In the former species, the antennal scrobe is more strongly impressed, and the frontal carina remains a distinct outside border of the scrobe.
Anterior view of head, adult worker. Cephalic dorsum with short lateral rugae intersecting longer longitudinal rugae. Separates all other Tetramorium species from T. caespitum_cf and T. tsushimae.	Close-up view of clypeus, adult worker. Clypeus lacking median notch.
Lateral view of body, surface characters, adult worker. Body is orange to reddish brown, except for gaster which is darker brown to black. Separates Tetramorium bicarinatum, some specimens of T. caldarium and some specimens of T. simillimum from other congeners.	Lateral view of body, surface characters, adult worker. Entire body is uniformly brownish yellow. Separates Tetramorium insolens, T. tonganum, some specimens of T. caldarium and some specimens of T. simillimum from all other congeners.
Lateral view of body, surface characters, adult worker. Erect hairs are sparse, short and stubby; never long and flexuous and never bifid. Used in Antkey to separate Tetramorium caldarium and T. simillimum from other congeners.	Close-up view of propodeum, adult worker. Propodeal spines short.
Lateral view of propodeum, adult. Propodeum spines are short, weakly developed and more closely resemble teeth or angles than long, well developed spines. Used in Antkey to separate species of Tetramorium.	Lateral view of petiole, adult worker. Petiolar node is relatively thick in profile. Used in Antkey to separate Tetramorium simillimum from T. caldarium. However, the usefulness of this character needs to be confirmed.
Lateral view of petiole, adult worker. Petiolar node is square shaped, with discrete and nearly flat anterior, dorsal and posterior faces. Separates Tetramorium bicarinatum, T. caldarium, T. caespitum_cf, T. simillimum and T. tsushima from other congeners.	Lateral view of petiole, adult worker. Petiolar peduncle is relatively thick in profile. Separates Tetramorium simillimum from T. caldarium. However, the usefulness of this character needs to be confirmed.