Zombie Caterpillar

Tobacco Hornworm caterpillars are very cool looking beasts, but they can be a garden pest, as they very much enjoy munching on one's tomato plants.

And the parasitoid wasp, Cotesia congregata, is quite happy in its larval stages to much on Tobacco Hornworm larva.

And these wasps, like the caterpillars they prey on, make cocoons from which the adults emerge. And the white objects seen in these images are those cocoons.

That's got to be unpleasant. First the adult female wasp lays its eggs inside the caterpillar, then the larva eat their fill emerging to create the cocoons.

And if that's not bad enough, the wasp enlists a polydnavirus, which prevents the caterpillar from forming its own cocoon and preventing metamorphosis. Turning it into a zombie of sorts. For all intents and purposes a walking dead food store for the wasp larva.

The virus cannot reproduce on its own, and needs the wasp's DNA to do so. Female wasps have special cells in their ovaries for producing the virus.

The caterpillar will continue to eat and eat, growing larger and larger, until it eventually dies. Which if you're trying to grow tomatoes is a good thing. These wasps are a natural method to control the caterpillars.

And for a science geek like me the complex life cycles are fascinating.

But it's incredibly creepy all the same.