Parasites do not have a positive reputation. I mean let’s face it; they live and feed on other living animals. They are considered cheaters, degenerates, thieves, evil things. And yet some of them do amazing amazingly complex things to earn a living, including brain surgery.

Let me introduce you to the Emerald cockroach wasp (Ampulex compressa), one of over 200,000 species of parasitic wasps on the planet. As the name implies, the Emerald preys on cockroaches in a very unique way. The female wasp first finds a victim, a large fat cockroach that is 5 times larger than she is. She ambushes the roach and they fight, tossing and tumbling about until the wasp is able to reach the cockroaches’ belly and delivers a sting, and the roach eventually goes limp. He is temporarily paralyzed for a few minutes, giving the wasp time to position herself over the roach’s head, and very precisely (using special sensors) inserts her stinger into just the right part of the brain, and delivers a special cocktail of drugs. Then she waits. The roach recovers from its initial belly sting, rolls onto its legs, and is perfectly capable of running away, but just stands there. It knows it should run, but all escape instincts are turned off. The brain sting has turned the roach into a zombie with no will of its own. The female then grabs one of the roaches’ antennae, gives it a tug, and the much larger roach responds like a puppet and follows like a dog on a leash. She leads him step by step to her burrow and parks him where she wants. She then lays eggs underneath his belly, seals up the burrow with rocks, and leaves. In a few days, the eggs hatch and hungry larvae emerge and drill their way into the roach's belly and begin feeding. They are careful not to eat vital organs that would kill the roach, feeding instead on body fluids and such. And still the roach just stands there. The young wasps finally pupate into adults, and like the gory scene in the movie Alien, burst out of the roaches’ body and fly off. And only then does the zombie roach die. Gives me the shivers.

We have several parasitic wasps in our area as well, the most famous being the dirt dauber, which uses paralyzed spiders as food for their young, but they are able to carry them to their nests instead of resorting to the zombie trick. Nature’s resourcefulness is amazing, and at times creepy.

By Steve Roark
TN Dept. Agriculture, Forestry Division