Question for Bug Furries: what's in the abdomen-tail?

I am a big fan of arthropod furries myself, and I think the abdomen-tail looks really neat, but today I wondered whats actually in that thing.

In real life arthropods the abdomen is full of guts and organs, but you'd expect all the organs in a humanoid body to fit inside the torso. Sort of a similar conundrum that Centaur anatomy has I guess, I'm curious if anyone else has an idea of what the deal would be with these bugs/arachnids/etc