Euw! Ed Yong has a gross-yet-cool post about parasitic nematodes that infect and kill caterpillars - and bring along luminous bacteria whose red glow is unpalatable to birds. If a bird eats the caterpillar host, the parasitic worms die. But the bacterial warning glow protects the worms' immobilized corpse home until they mature and burst out of the dead caterpillar - as grossly as possible, of course. (See photo on Ed's blog).
Natural, uber-gross bioephemera! Thanks, Ed. :)