I agree with Drapion and Gliscor. Kingler should remain Water type. It's a Crab, not a bug. For Crawdaunt, see Kingler. Kabutops does look somewhat bug-type, but I like to believe that its bug typing was replaced with rock when it fossilized.
Well, there's a bigger group bugs fall into in real life: the arthropods. Some animals, like spiders, crabs, centipedes, and scorpions are arthropods, but not bugs. And seeing that all spider and centipede Pokémon are bug-type, and you too think that the scorpions should be bug, too, I don't see why crabs wouldn't be. Also, the newest crab Pokémon, Crustle, is a Bug-Type.
Goemon, Simon Belmont, Mega Man, Paper Mario, Alex Roivas, Isaac, and Prince Sabure for SSB4! http://www.backloggery.com/krisi
I'd like to see a mosquito larva with a split evolution. Males would become special oriented with special-based draining moves (not sure about type). Females would become a physical Bug/Dark with biting moves and an ability that allows biting moves to drain health.