Synergistic toxin that induces or increases a cytolytic effect when combined with CSTX-1 (AC P81694) or CSTX-9 (AC P58604). When alone, has a weak insecticidal activity, with an unknown molecular target. Heterodimer of A and B chains; disulfide-linked (PubMed:15272079). Interacts with CSTX-1 (AC P81694) (Kd=430 nM), and with CSTX-9 (AC P58604) (Kd=370 nM) (PubMed:32290562). Expressed by the venom gland. The presence of a 'disulfide through disulfide knot' structurally defines this protein as a knottin. LD(50) is 16.3 pmol/mg in Drosophila. LD(50) is 111.2 pmol/mg when intrathoracically injected into drosophila. LD(50) is 0.075 pmol/mg when intrathoracically co-injected with CSTX-1 (AC P81694) into drosophila. LD(50) is 0.082 pmol/mg when intrathoracically co-injected with CSTX-9 (AC P58604) into drosophila. Does not show effect on 18 ion channels: Kv1.1, Kv1.2, Kv1.3, Kv1.4, Kv1.5, Kv1.6, Kv2.1, Kv3.1, Kv4.2, Kv4.3, Shaker IR, hERG, Nav1.2, Nav1.4, Nav1.5, Nav1.6, DmNaV1, and Cav3.3 (when tested at 500 nM on channels expressed in oocytes). Belongs to the neurotoxin 19 (CSTX) family. 12 subfamily.