Bioblimp

Its an older pic, but its kinda cool.

This larvae of this parasitic species floats high in the atmosphere. When it spots a potential host lower below, the balloon on its back rapidly deflates and it plummets claws-first downwards, like a javelin.

Just as it is about to strike its victim, the claws open out and tear into the hide, anchoring the creature. There it lives as a parasite on the larger animal and prepares to launch more floating larvae for the next generation.