Tetramorium caldarium

An increasingly common tramp species. Little is known about its biology and its influence, if any, on other ant species in the communities it invades. In India, this species is commonly found in disturbed regions with increased anthropogenic activities (Bharti and Kumar 2012), whereas in tropical and subtropical regions, populations are associated with greenhouses, zoos and heated buildings (Bolton 1980).

Identification
A member of the Tetramorium simillimum species group. Similar to Tetramorium simillimum. From the latter, it can be distinguished by the following combination of characters that contrast with what is found in T. simillimum: frontal carinae developed to the level of the midlength of the eyes behind which they become very weak or broken, or gradually fade out posteriorly, ground sculpture of head is feeble with surfaces dully shiny; antennal scrobes vestigial; the head behind the eyes does not broaden as it does in T. simillimum.

(Antkey: Guide to introduced ants) - Tetramorium caldarium is a small reddish 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. caldarium has two waist segments and a gaster armed with a stinger.

Wetterer and Hita-Garcia (2015) - Tetramorium caldarium workers are similar in body size, proportions, and color to another tramp ant species, Wasmannia auropunctata. Wasmannia auropunctata, however, is slightly smaller, has longer setae on the face and dorsum, longer propodeal spines, and a more rectangular petiole in side view. Another important key difference is the presence of a two-segmented antennal club in W. auropunctata compared to the three segmented club of T. caldarium. The latter also has very weak frontal carinae and reduced antennal scrobes while both of these characters are strongly developed in W. auropunctata.

Distribution
Tetramorium caldarium is believed to be native to Africa and is now widely distributed across the Pacific and other tropical regions. (Antkey)

Distribution based on Regional Taxon Lists
Afrotropical Region: Ivory Coast, Kenya, Saint Helena, Saudi Arabia, Socotra Archipelago, United Republic of Tanzania, Yemen. Australasian Region: Norfolk Island. Malagasy Region: Madagascar, Mauritius. Nearctic Region: United States. Neotropical Region: Barbados, Bermuda, Brazil, Colombia, Dominican Republic, Ecuador, Galapagos Islands, Greater Antilles, Guadeloupe, Haiti, Mexico, Peru, Puerto Rico. Oriental Region: India. Palaearctic Region: Balearic Islands, Canary Islands, Egypt, Germany, Iberian Peninsula, Monaco, Oman, Poland, Spain, United Kingdom of Great Britain and Northern Ireland.

Biology
Wetterer and Hita Garcia (2015) - Widely distributed by human commerce. Free living in tropical and subtropical areas, also found in temperate areas associated with people in protected areas, e.g., greenhouses, zoos, heated buildings. The sum of the occurrence records suggest this species is fairly arid-adapted and does not favor heavily shaded sites such as forests or woodlands. It can be found in natural and disturbed habitats. Despite its wide distribution there is no evidence their presence produces any significant ecological effects.

Regional Notes
Espadaler (2007) - Canary Islands: Collected only from two urban sites.

Bharti and Kumar (2012) - India: Collected from a disturbed area with high anthropogenic activities. It is widely distributed in the tropics and subtropics, associated with man and living in hothouses, zoos or other constantly heated buildings (Bolton 1980). It is uncommon in India and is here reported for the first time.

Deyrup, Davis and Cover (2000) - Florida: A relatively uncommon species occurring as far north as Hernando County. Most specimens are from open disturbed areas, usually near buildings. Pest status: none. First published Florida record: Bolton 1979.

Sharaf et al (2018) - Oman This species was found nesting under a rock where the soil was dry and loose and in an area cultivated rose plantations. Tetramorium caldarium was also collected among leaf litter in a well-irrigated public park.

Nomenclature

 *  caldarium. Tetrogmus caldarius Roger, 1857: 12 (w.q.) POLAND. Meinert, 1861: 331 (m.). Combination in Tetramorium: Bolton, 1979: 169. Junior synonym of simillimum: Roger, 1862c: 297. Revived from synonymy: Bolton, 1979: 169. Senior synonym of hemisi, minutum: Bolton, 1979: 169. See also: Czechowski, Radchenko & Czechowska, 2002: 68; Bharti & Kumar, 2012b: 21.
 * hemisi. Tetramorium pusillum var. hemisi Wheeler, W.M. 1922a: 193 (w.) DEMOCRATIC REPUBLIC OF CONGO. Junior synonym of caldarium: Bolton, 1979: 169.
 * minutum. Tetramorium minutum Donisthorpe, 1942a: 30 (q.) EGYPT. Junior synonym of caldarium: Bolton, 1979: 169.

Wetterer and Hita Garcia (2015) - T. caldarium was described by Roger (1857) from Poland, with the specimens collected from a greenhouse growing pineapples. This species was promptly (Roger 1862) synonymized under Tetramorium simillimum, where it remained until 1979 when Bolton revived its status as a valid species. Museum specimens of T. simillimum that do not have contemporary identifications need to be carefully evaluated to be sure they are not T. caldarium (see the identification section above for diagnostic characters).

Worker
Bharti and Kumar (2012) - HL 0.63-0.64, HW 0.53-0.56, SL 0.42-0.45, EL 0.12-0.13, WL 0.66-0.69, PW 0.37-0.38, PSL 0.03-0.05, PTL 0.13-0.14, PPL 0.18-0.20, PTW 0.18-0.19, PPW 0.21-0.23, PTH 0.20-0.21, PPH 0.18-0.19, CI 84.13-87.50, OI 21.82-23.21, SI 76.36-83.02, PSLI 4.76-7.94, PeNI 47.37-51.35, LPeI 61.90-70.00, DPeI 128.57-146.15, PpNI 55.26-62.16, LPpI 94.74-105.56, DPpI 110.53-127.78, PPI 116.67-121.05 (9 measured).

Head longer than broad, sides almost straight, posterolateral corners rounded, posterior head margin shallowly emarginated; clypeus consisting of flat basal half and steep apical half; anterior margin of clypeus entire without median notch; mandibles triangular, with 6 teeth, masticatory margin of mandibles with large apical and preapical tooth; third tooth slightly smaller than the preapical tooth followed by three denticles; frontal lobes weakly developed and elevated laterally, frontal area indistinct; antennal scrobes feeble, indistinct, very little concave and not bordered posteriorly; eye moderate in size, located laterally and almost at mid-length of head, composed of ca. 8 ommatidia in a series along its maximum length; antennae slender, 12-segmented; scape short from posterior head margin by one fourth of its length; mesosoma longer than head, broader anteriorly than posteriorly, dorsum flat and tapers to backward in lateral view; pro-mesonotal suture and metanotal groove indistinct; propodeal teeth small (PSL 0.03-0.05mm), acute, triangular almost equal to its width and propodeal lobes; propodeal lobes broad and roughly triangular in shape; posterior declivity of propodeum short, concave; petiole with a short peduncle, its node as broad as long with anterior and posterior faces parallel, weakly convex dorsum in lateral view; ventrally petiole weakly downcurved along its length; peduncle with a small anteroventral lamella; postpetiole broader than long, gaster oval.

Head feebly longitudinally rugose, interrugal space weakly granular or punctulate; frontal carinae feeble and developed to the level of the midlength of the eye behind which fade out or broken; mandibles weakly longitudinally rugulose; clypeus with a strong mid and two lateral carinae; dorsum of mesosoma weakly granular or punctulate with traces of rugulose sculpture; sides of mesosoma reticulate; petiole and postpetiole faintly rugulose and punctulate; propodeal declivity reticulate, upper half finely transversely rugulose, gaster unsculptured; legs smooth and shiny.

Whole body yellowish brown with gaster darker brown; body with short, erect, stiff, blunt hairs and few scattered pubescence on gaster; antennal scapes and hind tibiae with very short, fine, appressed pubescence.