I love Ed Yong’s blog, Not Exactly Rocket Science. He’s joined Alton Brown as a charter member of my Geeky Crush Club.
At the top of its plant, the caterpillar liquefies. Its body almost seems to melt. As it does, it releases millions of viruses, dripping them onto plants below and releasing them into the air. These viruses are the agents that compelled the caterpillar to climb, and eventually killed it. They are baculoviruses, and they cause a condition known aptly as Wipfelkrankheit – the German for “tree top disease”.
The baculoviruses are just some of the many parasites that change the behaviour of their hosts, and many of them trigger unusual tendencies to climb. The fungus Cordyceps unilateralis drives ants to bite into leaves around 25 centimetres above the forest floor. This zone has the perfect conditions for the fungus to develop its spore capsule, which erupts fatally through the ant’s head. Meanwhile, the Leucochloridium fluke cancels out a snail’s fear of bright lights, driving them to open spaces where they’re more readily eaten by birds – the fluke’s final host. Perhaps someday, scientists will decipher the genes that allow these parasites to take over minds as well as bodies.