Weak blocker of vertebrate P/Q-, N- and L-type voltage-gated calcium channels (Cav1 and Cav2) (By similarity). Is both paralytic and lethal when injected into lepidopteran larvae. Is not toxic to mice. Expressed by the venom gland. The presence of a 'disulfide through disulfide knot' structurally defines this protein as a knottin. Belongs to the spiderine family. Spiderine subfamily.