Do female black widow spiders kill and eat their mates after sex? July 7, 2020 by Pamela Landy Sometimes. What makes them decide to do so is uncertain. Related Answers When was Thanksgiving made a national holiday? How large is Deadwood, South Dakota? Who played The Merry Widow (1925) and whose widow was she? What was Squanto’s tribe in the winter of 1620? Who has been killing spiders since he was thirty? Who were Adlai Stevenson’s running mates in the 1952 and 1956 elections?