In Japan, nine species have been known in the ant genus Tetramorium, of which five or more are considered tramps. A key to the queens of nine Tetramorium species found in Japan is presented. The tramp species T. tonganum Mayr, 1870 is excluded from the key because no queen was available for us, while T. pacificum Mayr, 1870 is included because it was once intercepted at a port in Japan and exotic queens were available. Diagnosis of the queen of each species is provided together with differences between the two female castes. Tetramorium tanakai Bolton, 1977 is resurrected from synonymy with T. kraepelini Forel, 1905 based mainly on the queen characters.
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