Abstract: We present a morphology-based identification engine for ants of the Tetramorium caespitum/impurum complex, embedded in the world wide web. Using classificatory discriminant analysis the facility allows one to discriminate workers of nine very similar species, namely T. caespitum (Linnaeus, 1758), T. impurum (Foerster, 1850), T. hungaricum RÖSZLER, 1935, T. tsushimae Emery, 1925, and T. spp. A - E. Identification requires 21 characters, captured with high-precision morphometry. The identification engine includes verbal and graphic character definitions as well as an entry mask for morphometric data. Upon data entry, probability values for the sample's membership to each of the nine species are returned. We recommend users to apply and put on record a probability cut-off.