Many of the caterpillars are covered in stiff hairs. They practically sprint across the path. But another is slow, confused, trying to dig a hole. It has a smooth, velvety-looking body. No hair. But each and everyone of this kind has something else.
|Not the best photo, I'm afraid.|
See those little white things behind the head? Know what they are? They're wasp eggs. This caterpillar was parasitized by a parasitoid wasp. What, you ask, is that? A wasp laid its eggs on the caterpillar. When the eggs hatch, the wasp larvae will consume the caterpillar, eventually killing it.
The crazy thing is, the wasp eggs seem to have changed the caterpillar's behavior. Every other caterpillar was headed for high ground to spend the winter. All of the parasitized ones were trying to dig into the rocky path. Very un-caterpillar-like behavior.
Wasps often dig burrows where they stash a caterpillar with eggs on it. Parasitoid wasps don't disable their kids' future meal; they let the larvae take care of that. But something about the eggs must mess with the caterpillar's brain, changing its behavior in a way that will help the wasps, not the caterpillar.
It's been zombified.
Are there other zombies in nature? You bet. Entomogenous fungi do it, too. When the fungus takes up residence inside an insect's body, it eventually consumes the body tissues. In the process, it alters the insect's behavior.
|All that white stuff is the fungus. (source)|
Even rabies zombifies animals by putting them in attack mode. What better way to spread to new hosts than by hiding out in saliva and driving the current host into a frenzied, froth-mouthed state of attack?
Watch out for zombies this Halloween. You never know where they might turn up.
What is your favorite spooky critter?