Randy Spider

[urbeatle]

"You could create a caste that is, for all intents and purposes, a human, and another caste of the same creature that acts exactly like a giant cave spider, put the creature in a civ, and get a human-spider civ. The only flaw in this approach is that the castes will interbreed."

You say that like it's a bad thing...

(From a discussion of making a new civilization at the Dwarf Fortress Wiki.)