Most can be identified by a red hourglass on the abdomen . They are located throughout the United States. Its toxin causes nerve cell dysfunction and muscle cell twitching. Many have a violin-shaped marking on the chest. Both species are common in North America and throughout the world.
Contact is usually accidental.
Black widow bites may or may not have pain initially. Numbness, tingling, rashes, sweating, nausea, vomiting, dizziness, cramps, rigid abdominal muscles, chest tightness, weakness, and difficulty breathing may also occur. The abdominal pain often mimics pancreatitis or ulcer pain. Brown recluse bites are tender, red, swollen, and form blisters. Brown recluse bites cause local swelling, pain, itching, redness, tenderness, blisters, and eventually formation of a large ulcer.