and there was this spider down there with this amazing behavior: The male would apparently twist its body right into the female's mouthparts, and she would kill him while they were mating.

with species with less modified mouthparts exhibiting markedly less prey preference, and by their ability to extract key nutrients from their prey. The Lives of Spiders: A Natural History of the ...

They have piercing-sucking mouthparts, known as chelicerae, which they use to feed on plants. Adult TSSM also have two large dark colored spots on the sides of their bodies hence their common name.