Venomous creatures such as snakes and spiders are the stuff of human nightmares. Yet toxins are a regular part of the animal world, an essential tool for hunting and defense. A surprising variety of insects, reptiles, and amphibians use venom in their daily lives, either to subdue their prey or to prevent falling victim to another predator. Precisely how many forms of wildlife are venomous is only now becoming clear. From the mighty King Cobra, which...