The Black Widow Spider
For a long time, she has had a bad reputation for devouring her mate after copulation - a common predatory behavior in all (female) spiders. But many are unaware of the pain she unwittingly causes the male of the human species. For the good part of the first half of the 20th century, almost half of the black widow bites reported in medical journals were inflicted on the penis by spiders hiding under the outhouse toilet seat.
Since genitalia have an excellent blood supply, the black widow's venom, a neurotoxin, can spread to vital organs even faster.