Black widow spiders earned their name after scientists witnessed the females eat their mate after copulation. However, a closely related species- the Australian redback spider- have only been observed cannibalizing their mate about 2% of the time. What would cause their behavior to vary so drastically?
The black widow’s cannibalism was first observed in a lab, where males had nowhere to run from their larger counterparts. When in the wild, males generally won’t approach a hungry female, and attempt to make a quick getaway after copulation. This doesn’t mean females won’t turn down the opportunity for an easy meal, however!
Black widows are the most venomous spider in North America (but not the most venomous in the world). Their venom is approximately 15 times stronger than rattlesnake venom, and uses a special chemical to overwhelm nerve cells and cause immense pain. A bite can also cause swelling, cramping, fever and chills.
However, because of their small size, black widows can’t release much venom at once, and bites (while very uncomfortable) typically only pose a serious threat to young children and elderly people.