The Black Belly of the Tarantula is is a fairly boring giallo. The title alludes to wasps that paralyze insects, then lay eggs inside them - which is real, by the way; we even get to see stock footage of this in the movie - even though they call it a tarantula, it's actually just a spider.
A real, coked-up tarantula does make an appearance in the same scene, but it's only to push a pointless plot thread that a victim was involved with drugs.
I didn't like this movie, but I'll give it credit for giving us a real detective as the lead character, instead of some schmo playing gumshoe. We do briefly have Paolo playing vigilante, but [spoiler]that idiot gets thrown off a building, resulting in a very unintentionally-funny death.[/spoiler]
Pros: There's a nice amount of nudity in the movie. The killer stops to pet a kitty in one scene.
Cons: The kills are far too tame. There are moments of forced humor that just fall flat. The characters are one-dimensional.
This movie, like others with similar bad writing, needs to have a doctor explain the killer's motive to us, at the end - because it would make zero sense otherwise.