Omega-theraphotoxin-Hs2a blocks voltage-gated calcium channels (Cav) in adult cockroach DUM neurons. Reversibly paralyzes locusts and cockroaches, and causes death at high doses,. Expressed by the venom gland. The presence of a 'disulfide through disulfide knot' structurally defines this protein as a knottin. Its natural mutant mHwTx-V shows no effect on locusts, cockroaches, and mice. PD(50) of HwTx-V is 16 +/- 5 mg/kg to locusts. Has no effect on voltage-gated sodium or potassium channels in DUM neurons. Has no effect on mice by intraabdominal or intracerebroventricular injection (PubMed:18234186). Belongs to the neurotoxin 10 (Hwtx-1) family. 17 (Hntx-9) subfamily.