Their last evolution is induced by happiness and affection, is it not? Perhaps regularly working as a group to torment travelers and enjoy their fear is enough to trigger it. That said, I can only recall Zubats among their numbers.

[Not that his field of vision was particularly large up until a few minutes ago. He approaches the limit of the shield, looking around for any sign of the rest of his team.]

I could ask my Fire-types to end the hail with a Sunny Day, if there's no risk of awakening the unconscious ones.