“ Tetramorium caespitum ^HNS sensu lato”

Species morphologically similar to T. caespitum (Linnaeus ^HNS, 1758) are the dominant Tetramorium ^HNS ants in temperate parts of Eurasia. Cammaerts et al. (1985) distinguished T. impurum (Foerster ^HNS, 1850) from T. caespitum ^HNS in central Europe based on male genitalic characters. It has recently become clear that the T. caespitum ^HNS / impurum ^HNS species complex constitutes in fact an assembly of cryptic species, which cannot yet be delimited clearly or assigned valid names (Steiner et al. 2002; Schlick-Steiner et al., 2006). More than one species is included within the current concepts of both T. caespitum ^HNS and T. impurum ^HNS. Throughout this paper we use the term “ T. caespitum ^HNS s.l.” to denote species of the complex.