9:11am

Mon April 25, 2011
Animals

Where To Find The World's Most 'Wicked Bugs'

Japan is home to the world's largest — and most painful — hornet. With a wingspan of up to three inches, the Asian giant hornet can look more like a tiny flying bird.

And if you're a bird — or a bee — watch out.

The Asian giant hornet can inject "a deadly neurotoxin, [which] actually can be fatal," says science writer Amy Stewart. "In Asia, they call it a yak-killer because it has such a potent neurotoxin."

One entomologist in Tokyo described feeling like a hot nail had been driven into his leg after he was stung. The hornet has been known to prey on mantises and even other hornet species.

But the real danger is for honeybees.

"This is a very aggressive, murderous giant wasp," Stewart tells Fresh Air contributor Dave Davies. "It goes after their colonies, it kills them and it steals their honey."

To protect themselves, honeybees have developed a way to fight back. They lure the Asian giant hornet into their hive and fly around it at a rapid speed.

"[They] just sort of hover around them and tremble around them such that they raise the temperature [inside the hive] to exactly 116 degrees, which is just hot enough to kill the wasp without quite being hot enough to kill the honeybees," Stewart says. "So it's this totally bizarre insect defense with body heat that's otherwise unknown in the insect world."

Stewart examines the Asian giant hornet and more than 100 other creepy-crawlies in her new book Wicked Bugs: The Louse That Conquered Napoleon's Army & Other Diabolical Insects. From bat bugs — yes, bat bugs — to banana slugs to the pork tapeworm, she details the most infectious, most terrifying insects on the planet.

Bat Bugs: Violent Mating Habits

Take the bat bug — a parasitic close relative of the bed bug that only appears in homes with bat infestations. But after the bats are gone, the bugs have no problem biting humans and feeding on their blood.

"They will wander and find you," Stewart says. "And also, they have this violent, weird mating method. So even though I was trying not to be too hard on bugs for what they do to one another, I was rather appalled at the ways in which bat bugs mate."

Male bat bugs don't look for an access point to inject their sperm. Instead, they stab the female's abdomen repeatedly, trying to deposit their sperm directly into her bloodstream.

"As you can imagine, the females don't like this very much," Stewart says. "It's actually very hard on the females, and when you have colonies of bat bugs that are isolated in a laboratory — so the females can't get away — it kills them eventually. It's a very violent mating ritual."

To protect themselves, the female bat bugs developed a spongy, immune cell-filled structure — Stewart calls it a "false organ" — on their abdomen to accept the sperm without being repeatedly stabbed.

"That kind of worked, but what scientists discovered is that male bat bugs will actually go after other male bat bugs as well," she says. "So the males developed a similar and even better false organ to receive the sperm — which would be useless to them — so they could also avoid being stabbed. And then the females, seeing the males developed their own false organ, improved theirs, too. So there's all these strange gender-bending changes going on in the bat bug world, as it turns out. And I don't think it's over yet."

Worms Come In, They Don't Come Out

Bat bugs aren't the only parasitic insects Stewart describes in Wicked Bugs. She also profiles several worms — including the pork tapeworm — that feed off of host animals.

Pork tapeworms start out as larvae inside a pig. If the pig is infested, slaughtered and not cooked right, there's a chance the larvae could get inside a human body.

"The weird thing is that pork tapeworms have to get inside the body of a human in order to develop into the next stage of its life cycle," Stewart says. "No other animal works. We are called 'the obligate host' of the pork tapeworm."

Once inside a human body, the pork tapeworm settles inside the stomach, where it grows to adulthood, reproduces and waits — as long as 20 years.

"Adult tapeworms will eventually leave on their own or die," Stewart says. "But here's the thing: A person who is infected with tapeworms can spread those worms [or their] eggs to other people directly, without having to bother with a pig during the process."

That's one reason it's important to wash your hands after you use the bathroom, Stewart says — particularly if you handle food.

"When you swallow one of those eggs, instead of getting the larvae, then that little creature hatches and behaves very differently," she says. "It doesn't just settle in your stomach and start laying eggs — it travels all over your body."

Microscopic tapeworm eggs have been found all over the body — including the liver, lungs and brain.

"You actually have cases of people being diagnosed with brain tumors only to find out what they actually have is a tapeworm living in their brain," she says. "And what really astonished me is that tapeworms in the brain are the leading cause of epilepsy worldwide."

Zombie Bugs

The emerald cockroach wasp, also called the jewel wasp, is not a parasite, but it does abuse other creatures — particularly a certain species of cockroach in which the female likes to lay her eggs.

"She finds herself a good one, she stings it — and the sting paralyzes it for a minute — and she's able to get her stinger right inside the brain of the roach, that actually disables it from any instincts to run away," Stewart says. "It makes it this very docile, obedient cockroach."

The wasp is then able to lead the cockroach around and place it wherever she'd like it to be before laying her eggs in the cockroach's belly. After the larvae hatch, they eat the roach's interior organs and use its outer shell as a protective exterior.

Some might say that's a fitting end for the cockroach.

"We all hate cockroaches," Stewart laughs. "But entomologists are literally my favorite people in the world. For every bug, there is an entomologist somewhere who is more than happy to tell you about the lifetime of research they've devoted to that particular little insect. I had such a good time tracking down people who have spent their whole lives specializing and studying these insects." Copyright 2011 National Public Radio. To see more, visit http://www.npr.org/.