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The parasitic wasp, Dinocampus coccinellae, infects the beloved garden beetle, the ladybug, in a gruesome scene that could fit right into one of the Alien movies. First, the wasp injects a single egg into the ladybug’s abdomen. Upon hatching, the larva eats away at the ladybug’s tissues for approximately three weeks, at which point it paralyzes the ladybug by severing the nerves to its legs and digs its way out into the world. Remarkably, the ladybug remains alive after this, remaining immobilized as the larva spins a cocoon between its legs.
According to a study published online on June 22 in the journal of the Royal Society, Biology Letters, it’s in the wasp’s best interest to keep the ladybug alive in this zombie-like state for as long as possible. The researchers found that while the ladybug is paralyzed, it still acts as a bodyguard for the wasp while it’s in its vulnerable cocoon stage. Wasp cocoons that were sheltered by a living ladybug had only a 35 percent chance of being eaten by predators, compared to 85 percent if the ladybug was dead. Presumably, the beetle’s bright coloration and its secretion of toxic, foul-smelling liquids—both of which wane after death—serve to ward off the cocoon-seeking predators.
(This Halloween Nutshell was originally posted as an item in our behavior brief from June 30, 2011).