Latrodectus

Latrodectus is a genus of spiders in the family Theridiidae, commonly known as widow spiders. The genus includes more than 30 described species found in warm temperate and tropical regions worldwide. Notable species include Latrodectus mactans in North America, Latrodectus hesperus in the western United States and parts of Mexico, Latrodectus geometricus (the brown widow) in tropical and subtropical regions, and Latrodectus variolus in the eastern United States.

Female widow spiders are typically glossy black and larger than males, often bearing a distinctive red or orange hourglass-shaped marking on the ventral abdomen. Males and juveniles show greater color variation. Adult females may reach about 1–1.5 cm in body length, with proportionally long legs, while males are smaller.

Widows construct irregular, tangled webs in sheltered sites near the ground, such as rock crevices, debris accumulations, or human-made structures. They are usually nocturnal and prey on insects and other small arthropods, using their sticky capture threads to ensnare prey. They are generally shy and will retreat rather than bite unless disturbed.

The venom of Latrodectus contains latrotoxins that affect nerve transmission. Envenomation can cause severe pain, muscle cramps, and systemic symptoms, but fatalities are rare in healthy adults with prompt medical care. Treatment is mainly supportive; antivenom is available in some regions but is not routinely used. First aid focuses on immobilization and seeking professional medical attention.

Reproduction involves females laying eggs in silk sacs, which are often guarded by the female. Spiderlings emerge in large numbers and may disperse by ballooning. Widows are important ecological predators of pest insects but pose a bite risk in human-inhabited areas.