Crab is best because most are protected from whatever wasp has evolved specifically to end its life in mind boggling terrible ways.

Every 5th time it’s a beetle.

This is kinda backwards. Biodiversity is a result of random mutation over millions of years. Evolution is the result of selective pressures “choosing” from that diversity. It doesn’t create or provide biodiversity, it depends on it, so biodiversity should be the one providing crabs. Evolution just thinks they’re neat.