Spider, Widow

Widows are spiders from the genus Latrodectus, small but with a potent venon relative to its size, it have a preference for human houses as habitat, making a hazard for childrens and pets.

Biome/Spawn
There are 3 types of widows now:

Redback Widow (Latrodectus hasseltii) are Very Rare and spawn on any biome.

Northern Widow (Latrodectus variolus) are Very Rare and spawn on any biome.

Brown Widow (Latrodectus geometricus) will be added on next version, they also will be Very Rare and spawn on any biome.

Behavior
Widows will attack the beetles, but no other mobs.

Breeding
Yes; Spider Eye.