Well, Vandarus is male, and Wilda is female, so maybe it's the same species, but males are called Vandarus, and females are called Wilda.
in the show Wilda's voice is male
I said that before we've seen tht episode. And Bakugan.com says that Wilda is female, so I was going by thst until we found out. Now that we know Wilda is male, maybe Vandarus is female.