A unique 30-residue cationic peptide oxyopinin 4a (Oxt 4a) was identified in the venom of the lynx spider Oxyopes takobius(Oxyopidae). Oxt 4a con-tains a single N-terminally located disulfide bond, Cys4–Cys10, and is structurally different from any spider toxin studied so far.