Zimmer details the effects parasites have on their hosts--as well as the strategies hosts have developed to combat them. The book is rich with examples that would rival any sci-fi masterpiece.
"Every living thing has at least one parasite that lives inside it or on it," Zimmer states. He suggests that humans are parasitic in nature, feeding on the fruits of our planet's resources. "We humans exist within Gaia [the biosphere] and we depend on it for our survival. These days we live by using it up."
"If we want to succeed as parasites," Zimmer admonishes, "we need to learn from the masters." In some cases, it isn't the evolution of the predator that stuns the sensibilities, but the amazing and often disgusting adaptations developed by the apparent victims.
One such example: the Silver Spotted Skipper (a yellowish green caterpillar) is the target host for wasps, which inject their eggs into the caterpillar's body. The wasp larvae grow to maturity within the creature, waiting for the day when they can begin devouring the body from the inside, emerge, and continue their life cycles. After all, breakfast is the most important meal of the day.
The Silver Spotted Skipper has developed a unique strategy to avoid becoming a combination nursery and food storage unit for wasps. Wasps track down the Skipper using the stench of their feces. The Silver Spotted Skipper has developed a method to avoid detection. Using powerful anal muscles, called an anal cannon, the leaf dwelling Skipper blasts its feces distances from two to six feet, throwing wasps off its scent and eluding attack.
The leader in anal cannon research, Dr. Stanley Caveney, a zoologist at the University of Western Ontario, says the Skipper builds up a tremendous amount of blood pressure in its rectum--enough to explosively catapult the caterpillar-poop.
"You see that red face little kids get when they're sitting on the potty? A Skipper caterpillar does the same thing." Caveney says the blood pressure builds to such an extent that the "whole thing explodes, firing the pellets through the air."
As for his odd field of study, Caveney admits, "I'm actually trying to kill them because they're an agricultural pest, but that doesn't mean I can't have any fun."