<jats:p>The sting of the Neoguinean pseudomyrmecine ant, Tetraponera sp. (group punctulata) is modified in a structure resembling a drawing pen. These ants do not sting, but smear upon enemies a contact poison. The venom which originates from the poison gland is a mixture of eight alkaloids with an original tricyclic ring system. The structure of the major component, tetra-ponerine-8, has been determined by X-ray diffraction analysis. The poison of Tetraponera is highly efficient in deterring aggressive sympatric ants and tetraponerine-8 shows toxic properties against Myrmica rubra when applied topically, with a LD<jats:sub>50</jats:sub> of 5 × 10<jats:sup>-4</jats:sup> mg/mg of ants.