Tetramorium caldarium (Roger)

Bolton, B., 1979, The ant tribe Tetramoriini (Hymenoptera: Formicidae). The genus Tetramorium Mayr in the Malagasy region and in the New World., Bulletin of the British Museum (Natural History) Entomology 38, pp. 129-181 : 169-170

Tetramorium caldarium (Roger) stat. rev.

(Figs 28, 42)

Tetrogmus caldarius Roger , 1857: 12. Syntype worker, Germany: Prussia, Ananashause in Rauden' (BMNH) [examined] (previously treated as a synonym of simillimum , see note below). Tetramorium pusillum var. hemisi Wheeler, 1922: 193 . Syntype workers, Zaire: Niangara, stomach of frog (Hemisus marmoratum) (H. O. Lang) (MCZ, Cambridge) [examined]. Syn. n. Tetramorium antipodum Wheeler, 1927: 143 . Syntype workers, Norfolk I.: 1915 (A. M. Lea) (MCZ, Cambridge) [examined]. Syn. n. Tetramorium minutum Donisthorpe , 1942: 30. Holotype female, Egypt: Siwa, 17. vii. 1935 (J. OmerCooper) (BMNH) [examined]. Syn. n.

Note. Roger (1862: 297) synonymized his species Tetrogmus caldarius with Tetramorium simillimum , the latter being the senior name. His genus Tetrogmus rightly disappeared into the synonymy of Tetramorium but since then the name of the species which he described has consistently been referred to the synonymy of simillimum , where I left it in the second part of this study (Bolton, 1977). Since then the taxonomy of the simillimum-group has been studied in greater detail and it has become apparent that caldarium is a valid species, close to simillimum but consistently differing from it in the structure of the frontal carinae and in other details. From this finding T. caldarium is henceforth removed from the synonymy of simillimum and stands as a good species.

Worker. Basically similar to simillimum and agreeing with the description of that species in most particulars, but differing as follows.

1. Frontal carinae less strongly developed. Generally the frontal carinae of caldarium are feeble throughout their length and usually weakly or not sinuate. They are best developed to the level of the midlength of the eye, behind which they become weak or broken, or fade out posteriorly, becoming indistinguishable from the cephalic rugulae in many cases. The low, raised flange or rim, which runs almost the length of the carinae in simillimum , is much weaker in caldarium and only developed to a level about equal to the midlength of the eye, behind which it quickly disappears.

2. Antennal scrobes feeble. In simillimum the antennal scrobes are shallow but are long and broad and distinctly concave, the effect being enhanced by the strong frontal carinae which delimit their dorsal and posterior margins. In caldarium the scrobes are much more weakly developed, very little concave and not bordered posteriorly. Also, the poor development of the frontal carinae makes the scrobes look very nondescript. Compare Figs 41 and 42.

3. Cephalic ground sculpture weak. In caldarium the strong reticulate-punctulation or granulation seen in simillimum is replaced by a much weaker granular or punctulate ground-sculpture between the rugulae, so that the head appears by no means as matt and rough.

4. Head differently shaped. In simillimum the head in full-face view tends to become broader from front to back, the sides diverging behind the level of the eyes, whereas in caldarium the width of the head does not noticeably increase posteriorly, compare Figs 41 and 42.

These characters in combination will differentiate the two species in the New World. The species will be treated in more detail in the part of this study dealing with the fauna of the Ethiopian region, as both have a number of closely related forms in that zoogeographical region.

Apart from the New World references given below, caldarium is widely distributed in Africa from Egypt to Kenya and occurs sporadically on islands such as the Cape Verde group, Mauritius, Madeira and St Helena. Occasionally it is introduced in Europe as the types from Germany and a series from Kew Gardens, London go to show, but it is hard to assess how often it is introduced or how successful the species is as no doubt many of the past identifications of simillimum in Europe should in fact have been referred to this species. T. caldarium is not known from Australia and seems to be uncommon throughout the Oriental and Indo-Australian regions. Three series are known from India but apart from this the only records of caldarium are the series from Norfolk Island which make up the types of the synonymous antipodum and three workers from New Caledonia.

In part two of this survey (Bolton, 1977: 131) I gave antipodum as a provisional synonym of simillimum as at that time I had not been able to locate any members of the type-series. Since then a number of specimens referable to the type-series of antipodum have been found in the collections of MCZ, Cambridge and these show the species to be a straight synonym of caldarium .

Material examined (New World)

U. S. A.: Florida, St Augustine (W. L. Brown). Mexico: Rio Metlac, Veracruz Canyon (A. Newton); Nogales; Guerrero, Chilpancingo (N. L. H. Krauss). Puerto Rico: Mayaguez (M. R. Smith); Tres Hermanos (M. R. Smith); Coamo Springs (W. M. Wheeler). Haiti: Furcy (W. M. Mann). Dominican Republic: series on logs ex Dominica, intercepted at New York. Colombia: series on orchids ex Colombia, intercepted at New York (S. D. Whittock). Brazil: SP., Paracicaba (C. A. Triplehorn). Peru: Chaclacayo, E. Lima (H. Crozier).