Nature is certainly amazing, but this is almost unbelievable:
The parasitoid wasp Glyptapanteles lays its eggs, about 80 at a time, in young geometrid caterpillars. The eggs hatch and the larvae feed on the caterpillar's body fluids. When they are fully developed, they eat through the caterpillar's skin, attach themselves to a nearby branch or leaf and wrap themselves up in a cocoon.
At this point, something remarkable and slightly eerie happens. The caterpillar, still alive, behaves as though controlled by the cocooned larvae. Instead of going about its usual daily business, it stands arched over the cocoons without moving away or feeding. The caterpillar - now effectively a zombie - stays alive until the adult wasps hatch.
"We don't know exactly what kills the caterpillars, but it is fascinating that the moment of death seems to be tuned to the duration of the wasp's pupal stage," says Arne Janssen of the University of Amsterdam.
To test the manipulation hypothesis, Janssen's team allowed wasps to infect caterpillars in a laboratory setting. Once the larvae emerged and formed their cocoons, the researchers separated half the cocoons and the caterpillars. The separated cocoons were attached to a leaf next to an unparasitised caterpillar, which was prevented from moving away by a ring of insect glue around the stem.
When they added a stinkbug, a voracious predator of wasp cocoons, the team found that 17 of the 19 parasitised caterpillars thrashed their heads around in the direction of the bug. More than half the time, this knocked the bug off the branch or made it retreat. Unparasitised caterpillars barely noticed the bug, even when it climbed on top of them.
To see if the behaviour affected the survival of wasp cocoons in the wild, the researchers placed over 400 parasitised caterpillars in guava fruit trees one day before the larvae were due to break through their skin. Once the larvae had cocooned themselves on the nearby branches, the researchers removed half of their bodyguard caterpillars and watched what happened. The survival rate of "guarded" cocoons was twice as high as that of unguarded cocoons.
I wonder how many chance mutations must have occurred in both the wasp and the moth in order for this behavior to evolve. Now don't get me wrong. I'm not saying that this wonderful dance of wasp and caterpillar is not just a result of natural processes acting blindly over long eons of time. I'm not saying that stuff like this suggests that there must have been some kind of intention somewhere along the way. I'm not saying that lots of random mutations at just the right time, together with natural selection, can't all by themselves work miracles. I've read my Dawkins, and I'm sure they can, but still....
RLC
