First blocker of sodium channels (Nav) found in scorpions. Is lethal to crustaceans (Cambarellus montezumae), less toxic to insects (crickets) and non-toxic to mammals (mice) at the doses assayed. Expressed by the venom gland. Has the structural arrangement of an alpha-helix connected to antiparallel beta-sheets by disulfide bonds (CS-alpha/beta). Belongs to the long (4 C-C) scorpion toxin superfamily. Sodium channel inhibitor family.