Just in time for Halloween is a scary article about parasites that control their hosts' behavior in the November 2014 issue of National Geographic, "Mindsuckers: Meet Nature's Nightmare" by Carl Zimmer.
Let's meet some ant relatives, the parasitic wasps, and learn how they turn their hapless arthropod hosts into "zombies."
"It is as astonishing as it is sad to watch a ladybug turn into a zombie. Normally ladybugs are sophisticated and voracious predators. A single individual may devour several thousand aphids in a lifetime. To find a victim, it first waves its antennae to detect chemicals that plants release when they’re under attack by herbivorous insects. Once it has homed in on these signals, the ladybug switches its sensory scan to search for molecules released only by aphids. Then it creeps up and strikes, ripping the aphid apart with barbed mandibles.
Ladybugs are also well protected against most of their enemies. Their red-and-black dome, so adorable to the human eye, is actually a warning to would-be predators: You will regret this. When a bird or some other animal tries to attack, the ladybug bleeds poison from its leg joints. The attacker tastes the bitter blood and spits the ladybug out. Predators learn to read the red-and-black wing covers as a message to stay away.
A predator protected from other predators, the ladybug would seem to have the perfect insect life—were it not for wasps that lay their eggs inside its living body."
The article goes on to talk about how a parasitic wasp feeds on the lady beetle, controlling it in a gruesome way.
As you would expect from National Geographic, the photographs in the November 2014 article are fantastic and chilling, all in one.
(Photograph © by Anand Varma/National Geographic; Jacques Brodeur Lab, University of Montreal, copyrighted image used with permission).
"Parasitic Wasp Dinocampus coccinellae
Spotted Lady Beetle Coleomegilla maculata
Ladybugs are said to bring good luck—but one infected by the wasp species Dinocampus coccinellae is decidedly unfortunate. When a female wasp stings a ladybug, it leaves behind a single egg. After the egg hatches, the larva begins to eat its host from the inside out. When ready, the parasite emerges and spins a cocoon between the ladybug’s legs. Though its body is now free of the tormentor, the bug remains enslaved, standing over the cocoon and protecting it from potential predators. Some lucky ladybugs actually survive this eerie ordeal."
What is that glowing golden object on the spider's back? It turns out that even spiders are not immune.
(Photograph © by Anand Varma/National Geographic. Copyrighted image used with permission.)
"The spider Leucauge argyra suffers a series of humiliations at the hands of the parasitic wasp Hymenoepimecis argyraphaga before it is put out of its misery. Paralyzed by the wasp’s sting, the spider stands helpless as its tormentor deposits an egg on its abdomen. Once the egg hatches, the larva holds tight to the spider like some malignant piggybacker, feeding on its internal fluids for a week. When ready to pupate, the larva coerces the spider into setting out on one last, misguided building project. Ripping down its own carefully constructed web, the spider spins a novel one consisting of just a few thick crossing strands. The larva rewards the spider for its efforts by sucking it dry. Then it spins its cocoon at the intersection of the two strands, where it can dangle safely out of reach of predators."
(Images and text are from the November 2014 issue of National Geographic magazine.)
The article goes on to discuss several other examples and the evolutionary significance of these bizarre lifestyles. If you are a biologist, especially an entomologist, you are probably familiar with some of these examples, but perhaps not all of them.
Reading the article does give me some ideas for awesome Halloween costumes.
What do you think of the Mindsuckers article? Do you think the tie-ins to popular culture help foster science communication or do you think it confuses the lay audience?
Thank you to Lauren for bringing this article/opportunity to my attention.