Throughout science fiction and horror films and literature, a recurring and rather popular theme has always been that of the evil alien puppet masters that control our minds to hold us in thrall to force us into servitude to our overlords or to take over our bodies to turn us into something else. This simple concept has been popularized in stories and films such as The Puppet Masters and Invasion of the Body Snatchers, and these stories have horrified generations. The thought of having our minds and bodies defiled and invaded and made to act in service of another against our will is an innately unsettling thought which both repulses us and yet inspires a certain macabre curiosity that keeps us coming back for more. As terrifying as it may be, it is perhaps even more horrific to think that such organisms are far from merely the denizens of fiction, and the animal world actually has a disturbingly large number of creatures who survive by taking over and controlling the minds of others, often leading to the victim's doom.
Perhaps the most well-known mind-controlled zombies of the animal world can be seen in insects, and one of the most horrific happens to certain types of ants. The culprit is several species of parasitic fungus belonging to a genus called Ophiocordyceps, and its life cycle is just about as terrifying and disturbing as anything from a horror movie. It starts with the fungus spores entering the ant and causing it to experience a fit of convulsions that sends it reeling and tumbling to the forest floor. This is not by far the end of the process, as the fungus actually begins to take over the ant’s mind and changes its behavior, forcing it to mindlessly begin climbing up a branch or stem to a predetermined height depending on the fungus species, where the horrors continue.
Once atop the plant, the parasite forces the “zombified” ant to face a specific direction and find a certain spot where the humidity is just right, again depending on the species, after which the ant is made to clamp down as hard as it can onto the stem by its new overlord master. As it does this fungal spores are accumulating within the ant, culminating in a stalk erupting from the head to rain down spores across the ground below in a shower of death, infecting other ants to in turn suffer the same fate. Throughout the whole gruesome process the ant’s jaw never releases its grip, leaving its exploded, withered corpse and its outlandish alien stalk projecting from its head to remain there waving in the wind.
It is incredible that this fungus is able to get inside the ant’s head and manipulate it with such astounding precision, and each species of Ophiocordyceps targets a different species of ant and its unique behaviors in a stunning display of coevolution. Scientists do not yet fully understand how this zombie fungus manages to do what it does, but it is likely through manipulating certain enzymes and chemicals within the ant’s brain to hijack their nervous system through processes that remain unclear. The whole process is gruesomely chilling, and just about the only good news about it is that there is no version for human beings.
Another insect that is the target for horrors beyond comprehension is the colorful and charming ladybug. If one of these ladybugs is unlucky enough, it might run across a type of wasp known as the green-eyed wasp (Dinocampus coccinellae), which specifically hunts them down for its nefarious purposes with a two-pronged attack. Upon finding a suitable target, the wasp uses its stinger to inject both an egg and a virus. As the egg grows into a larva it feeds on the ladybug’s insides to sustain itself, while the virus gets to work shutting down the insect’s brain functions to essentially paralyze it, and one might think that that would be the end of that, but it’s only just beginning.
The wasp larva grows within the still-living ladybug until it is large enough to violently burrow its way out, upon which the ladybug is still alive. The wasp larva spins itself a cocoon, and this is where the virus enters a sort of second stage, making the ladybug spring back to life and stand up, putting it into a sort of trance-like state to watch over the very thing that has just erupted from its innards. If a potential threat comes too close, the virus causes the ladybug to jerk and lurch, chasing it away, and it does this until the young wasp is ready to fend for itself. It seems like this must not end well for the zombified ladybug, but interestingly enough around a quarter of the victims of this macabre process actually survive it and go on to lead normal lives.
There is also the plight of the cicada, which can fall prey to a type of parasitic fungus that turns them into uncontrollable raging zombies out to infect others of their own kind. Upon being infected with the fungus, the male cicada will find its abdomen and genitals wither and fall off, while conversely experiencing a major surge in sex drive. The cicada is possessed and compelled by the fungus to basically chase after any tail it can get its hands on, mating left and right with anything and everything, all the while spraying the fungal spores onto new hosts in the process, earning them the rather colorful nickname among scientists "the flying salt shakers of death."
Moving away from insects we have caterpillars, which fall prey to the parasitoid wasp Glyptapanteles. After being stung, the caterpillar becomes absolutely, insatiably ravenous, eating far more than usual and fattening itself up for the larva inside it to feed off of. In a very similar process to what we saw in the ladybug above, the wasp lays its egg within the wasp, the larva grows and pops out, and the caterpillar is zombified and turned into a mindless, thrashing bodyguard to keep predators away. Taking things a step further, the caterpillar is also compelled to spin more silk around the wasp’s cocoon, reinforcing its armor barrier, and it will stand guard there by its charge until the wasp can go off on its own or until it starves to death. It never ends well for the caterpillar. Almost as bad is a type of baculovirus that infects the gypsy moth caterpillar to force them to climb high up into trees, where they more or less disintegrate to send the virus raining down upon other caterpillars.
In other example of yet more types of mind-controlling parasitoid wasp, we have some that target spiders to change their behaviors for their own benefit. One type of wasp from Costa Rica is called Hymenoepimecis argyraphaga, which prowls about looking for orb weaver spiders to inject with its eggs. When this is done, the larvae grow and emerge, but remain attached to the still living spider as a sort of unwelcome hitchhiker. The weird part is that when it is time for the wasp to spin a cocoon it hijacks the spider’s brain to do it, commanding the spider to spin the cocoon around it rather than do all that work itself, after which they rather ungratefully eat the spider. Similarly, the Zatypota wasp of Ecuador lays its egg into a victim of the spider species Anelosimus eximius, which is usually a social species that hangs out in communal colonies. However, when impregnated by the wasp larva the spider is mind-controlled to leave the colony and trek out in its own, where it then finds itself spinning a cocoon to protect it and its tormentor and allow the wasp to devour it in peace.
There are several types of parasitoid wasps like this targeting spiders that also manipulate their hosts in shockingly sophisticated ways. One type of wasp native to the rainforests of Costa Rica (Costa Rican spiders get no breaks) targets the species of spider Anelosimus octavius as its host. This type of spider generally weaves knotted, gnarled webs of haphazard threads, but infected individuals will go off and spin webs that are completely different in design. Infected spiders essentially have their brains hijacked into weaving webs that have a platform covered by sheets of webbing that protect it from the rain and elements, as well as an odd opening at the end of the platform. When these bizarre webs are finished, the wasp larvae emerges from the spider, killing it, makes its way to the end of the well protected platform, and hangs from a cocoon through the opening that the spider has graciously provided. It is extraordinarily creepy that this parasite can not only alter its host’s behavior, but also essentially have it act as its own personal architect.
Rather than turning their hosts into protectors or bodyguards or killing their victims directly, many of the mind-controlling parasites and parasitoids out there are fine tuned to making their victims suicidal, changing their behavior to intentionally put them in peril so that they can be eaten and their life cycle can be completed. A good example is a parasitic flatworm known as Leucochloridium paradoxum. It spends most of its life living within birds such as robins, but it needs snails to complete its entire lifecycle and it is pretty complicated. First an infected robin defecates onto the ground, after which a snail will come along and be infected by eating the droppings. The parasite larva then go about engorging the snails head tentacles to make them a vivid bright color that is easy to spot in contrast to the snail’s usual drabness. After this, the parasite controls the snail’s mind to make it climb atop a high point and wave about its tentacles about in a pulsating display of vibrant color, the sole purpose of which it to attract a robin, which swoops down to peck at the irresistible lure and is thus infected with a parasite to start the cycle anew. The snail is essentially modified by the parasite into a suicide bomber with a death wish to deliver its insidious payload.
A similar process can be seen with parasitic worms called acanthocephalans, which also live most of the time in the intestinal tract of birds, in this case starlings, but seek out pill bugs, better known as “roly polies,” to complete part of their lifecycle. Like with the snails, the bird’s droppings contain microscopic eggs that mix in with the pill bug’s usual diet of deteriorating vegetable matter and are ingested to infect the host. The larvae quickly zombify the pill bugs and radically change their behavior. Whereas these creatures are usually very shy and hide in dark crevices and under rocks or logs, the infected instead brazenly and fearlessly go right out into the open in broad daylight and act erratically, as well as to actually seek out light colored surfaces to roam about on in contrast to their dark coloring, all the better to lure in a predatory starling.
The same kind of thing can be seen in the killifish of California, which is infected by a type of fluke that also cannot wait to get into a bird, which is its preferred habitat and where it matures. It order to get from down here up to there, the fluke invades the host’s brain and makes them do all sorts of weird and reckless things. The infected killifish, which would normally stay away from the surface and be very wary, is instead drawn to the light, restlessly swimming just under the waves and will also flick its tail at the surface to fully advertise its presence to any seabirds that may be around, in the process being eaten and infecting them. This is very similar to the thorny-headed worm, which enters the mind of a type of crustacean called a gammarid to make the normally skittish creature seek out the light of the surface and swim around erratically so that it may be eaten by a duck, where the worm really wants to be.
There is a perhaps even more frightening example of this in the animal kingdom, simply because it doesn’t happen to some small insect, bug, or fish, but rather a mammal or bird. One parasite which can also alter behavior in animals is Toxoplasma gondii, which is usually found in rodents such as rats, as well and small birds. Animals infected with the parasite will lose all fear of their natural enemies, and rather than flee from predators such as cats will feel compelled to run or fly right towards them. This of course leads to the rat or bird being eaten and the parasite carrying out the rest of its life cycle through the cat and its feces. This infects humans too, and while it is unclear just what effects humans have when infected with Toxoplasma gondii, there has been debate that it causes everything from no effect at all to major behavioral aberrations and schizophrenia, but it is at this point it is largely unknown.
It is a horrifying but at the same time fascinating world that these organisms inhabit, with complex relationships developed through incredible instances of co-evolution between completely disparate species developed over millions of years and powered by processes we have yet to fully understand. While zombies and mind-controlling puppet masters as depicted in the movies and fantasy books may always remain in the realm of fiction, these real life examples of this happening to some extent in the animal world are a sobering thought, and create both a sense of wonder and terror, and one can only hope that humans do not become victim to such creatures. For now, we are safe, but they will certainly stalk our nightmares and influence science fiction and horror for some time to come.