The following is an excerpt from NationalGeographic.com.
We've known for years that female black widow spiders and other arachnids eat males during mating.
Now, new research shows that males of a type of ground spider known as Micaria sociabilis also eat females, and scientists are trying to figure out what motivates this behavior.
A male M. sociabilis attacks his mate. Photograph courtesy Lenka Sentenská
More than just a first date from hell, sexual cannibalism happens when one member of a species kills and eats a member of the opposite sex immediately before, after, or during mating.
This behavior is most common in arachnids like the black widow, as well as other invertebrates like insects, gastropods, and copepods. Most commonly, the female eats the male-but occasionally, the reverse is true. Male sexual cannibalism has been observed in another species of spider, Allocosa brasiliensis, and in crustaceans, but previously researchers had no idea what factors drove this behavior.