Mindy Weisberger (Johns Hopkins University Press)
A snail, eyestalks pulsing with coloured stripes, leaves the safety of the shade and oozes its way onto an exposed leaf, where it catches the beady eye of a bird. The larger animal mistakes those eyestalks for delicious caterpillars and pounces; in the process, it accidentally gobbles up the parasitic worms infesting the Succinea putris snail.
This poor mollusc is far from alone: worms, wasps and other creatures that manipulate their hosts鈥� behaviour are common in the invertebrate world. In Rise of the Zombie Bugs: The surprising science of parasitic mind-control, science writer Mindy Weisberger examines the ways these tiny monsters hijack the bodies and brains of their victims 鈥� and how they have captured our imaginations.
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Zombies are a major trope in fiction, recognised throughout Weisberger鈥檚 engaging book, which is full of nods to their many guises and features quotes from zombie stories, films and TV shows to start each chapter. We can even learn a bit about real parasites from these yarns: take The Last of Us and its zombifying fungus; or Alien, whose chest-bursting 鈥渪enomorph鈥� has a counterpart in zombifying wasps.
But real zombie species have something their fictional counterparts lack: sex appeal. Many fungus-infected insects attract mates, who inevitably leave the tryst with their own burgeoning infestation. In fact, the zombifying fungus Entomophthora muscae makes its victims more attractive 鈥� to the point where some experiments showed male fruit flies mating with fungus-stuffed corpses rather than living females.
In that case, writes Weisberger, the fungus releases compounds that attract would-be mates, using these signals to control not only its host, but the other insects around it. That isn鈥檛 the only mechanism such parasites use, however. They also manipulate the muscles of victims, modify the hormonal signals that regulate their development and flood their brains with behaviour-modifying chemicals.
Weisberger explores in great detail the experiments attempting to unravel these mechanisms. Her attention to the scientific aspects of zombification can be a positive 鈥� as a horror wimp, I was reassured when she explored if humans could ever fall victim to these zombifying mechanisms. But her narrative can be overly technical and repetitive.
Part of that is beyond her control. Despite the fact that zombie insects are everywhere 鈥� some are so common researchers can collect and study specimens from their own backyards 鈥� many of the parasites that infect them use similar tricks. Zombified insects, for example, commonly climb to unusual heights before releasing infectious material on their brethren below.
Fungus-laden ants reach the high ground by clambering up and using their jaws to grip a leaf, while infected cicadas soar overhead like 鈥渇lying salt shakers of death鈥�, according to a researcher quoted by Weisberger. And while even healthy caterpillars ascend trees to eat, some virus-infected ones fail to go back down, instead melting into dripping, infectious goo. Sure, those are all grisly ways to go 鈥� but each time I read about deadly material raining out of yet another insect鈥檚 corpse, it felt a little less horrible and a little more, well, normal.
For me, the real pulse-pounding action comes when Weisberger offers a glimpse of the organisms that manipulate mammals, from the rare but terrifying rabies virus to the surprisingly common Toxoplasma gondii protozoan, which infects at least 30 per cent of pet cats. And she touches on the ways that zombie species offer a genuinely useful window into the spread of infectious diseases.
Rise of the Zombie Bugs is a great read, but it didn鈥檛 get under my skin quite as much as its author might have hoped.
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