(The molecule serotonin is best known in humans as a target of anti-depressant drugs. I always thought they were two different species. One nice little green one who never did anyone any harm, and the other a rapacious beasty to be stomped on, but seemingly prior to swarming, the locusts undergo a series of dramatic physical changes - their body colour darkens and their muscles grow stronger for flying. The daft thing is that the change takes place when food becomes short, and they slowly start to cluster together and before you know it there's a real food shortage. Isn't nature weird?)






