Black widows in the genus Lactrodectus (or closely related groups) are found throughout much of the world.   All spiders are venomous, but the female black widow is one of very few spiders that has the capacity for doing serious damage to a person.   Like most venomous animals, they are rather timid and will attempt to escape if disturbed, but if handled or pinned, they can inflict a very painful bite that -- very, very rarely -- can be fatal.   These spiders are frequently common in sheltered areas (in dark corners, woodpiles, trash, etc.) and I probably have several living in my garage at any time.   Easily recognized by their shiny black abdomens with red marks on the underside, the females make papery silk egg-sacs (upper left) containing dozens of eggs that hatch into tiny but well-formed spiderlings (upper right).   I took these pictures in a colleague's laboratory at the University of California, Riverside.