A single drop of black widow spider venom is potent enough to kill 2,000 mice.

The primary active component in black widow venom is a large protein called alpha-latrotoxin. This toxin specifically targets the presynaptic nerve terminals of vertebrates, triggering an uncontrolled release of neurotransmitters including acetylcholine, norepinephrine, and GABA. This massive chemical surge causes the victim's nervous system to go into overdrive.The potency of black widow venom is measured using the LD50 scale—Lethal Dose 50 percent—which indicates the amount needed to kill half a test population. For the black widow (Latrodectus mactans), the LD50 is approximately 0.9 milligrams per kilogram in mice. Because a single drop of venom contains a high concentration of these proteins, it can theoretically overwhelm the nervous systems of thousands of small rodents, making it one of the most toxic biological substances in the animal kingdom.Despite its fearsome reputation, the black widow is not naturally aggressive toward humans. According to the American Association of Poison Control Centers, thousands of bites are reported annually in the United States, yet deaths remain incredibly rare. The last recorded death from a black widow bite in the U.S. occurred decades ago. This is because the volume of venom delivered during a defensive bite is usually insufficient to cause systemic failure in a large mammal.Medical treatment has advanced significantly since the early 20th century. Doctors typically treat severe cases with calcium gluconate to manage muscle cramps or a specific antivenom derived from horse serum. Most healthy adults recover within three to five days with supportive care. The combination of low venom volume and effective modern medicine ensures that this deadly spider remains a manageable threat.