Varroa Mites Are a Honeybee’s 8-Legged Nightmare
Every year, up to half the honeybee colonies in the U.S. die. Varroa mites, the bees’ ghastly parasites, are one of the main culprits. After hitching a ride into a hive, a mite mom hides in a honeycomb cell, where she and her offspring feed on a growing bee. But beekeepers and scientists are helping honeybees fight back.
TRANSCRIPT
Here’s a go-to recipe for beekeepers. It’s called a “sugar shake.”
Take a half-cup of bees. That’s about 300.
Put them in a jar and cover them with a mesh lid.
Add two tablespoons confectioners’ sugar.
Shake for 30 seconds. We’re going for a nice, even coat.
Empty the sugar onto a tray. And there you have it: frosted varroa mites, aka Varroa destructor. They’re a honeybee’s worst enemy.
The fine-powdered sugar made them lose the grip they had on their hosts.
A minute ago, the mites were on the bees in the hive.
It’s as if you were carrying around a tick the size of a dinner plate.
Every year, up to half the managed honeybee hives in the United States die from hazards like pesticide exposure, lack of flowers to forage on year-round, and varroa mites.
To feed, a varroa mite nestles between the bees’ protective plates.
It digs in with its gnarly mouth, the gnathosoma. The mite sinks it into a crucial organ called the fat body. It’s a layer of tissue that lines the abdomen.
Sort of like the human liver, the fat body helps the bee break down harmful stuff, including pesticides. And it maintains the bee’s immune system. So, when varroa mites attack the fat body, they seriously weaken the bee.
The mites can also transmit a virus that causes a bee to be born with deformed wings, no good for flying.
Let’s go back to the “sugar shake.” Beekeepers use them to monitor the varroa mites in their hives.
As few as three mites per half-cup of bees could kill a hive within the year. That’s because varroa mites are great at sneaking into hives, hiding, and reproducing like mad.
The first mite gets into a hive by hitching a ride on a bee from another colony. Maybe the bee’s own colony wasn’t doing well and it was looking for a new home.
The mite sniffs around for a bee larva and sneaks in right before the bees cover the cell with wax.
The defenseless larva is now trapped with its enemy, which begins to feed.
As the larva grows into a pupa, the mite, called a foundress, starts her family. Take a look underneath this bee pupa.
The mite’s firstborn is always a son. The rest are daughters. They’re hard to tell apart when they’re young.
When the siblings come of age inside the cell, they’ll meet up on this pile of mite poop – maybe they’re guided by the scent. And they’ll mate … with each other.
Sometimes two foundresses make it into a cell. Then their offspring get to mate with someone they’re not related to.
The mites live off the bee pupa, but they don’t kill it.
When the bee is all grown up, it chews its way out of the cell.
The mite slips onto its next victim.
So, why don’t the bees just pick those mites off themselves?
Well, we didn’t start seeing varroa mites in the U.S. until the 1980s. They evolved on eastern honeybees, in Asia. That’s why the western honeybees in the Americas and Europe aren’t yet good at defending against them.
When beekeepers find mites in a sugar shake, they treat a hive with pesticide strips that kill the mites. But mites are becoming resistant.
So, researchers are selectively breeding honeybees to fight back.
The U.S. Department of Agriculture and private companies are breeding bees that can sniff out varroa mites. When the bees find some, they uncap the cells and interrupt reproduction. The bees then, um, “recycle” the unlucky pupa. Yep, they’re eating it.
At Purdue and Central State universities, scientists breed honeybees known as “mite-biters.”
After collecting sperm from a male bee, they inseminate a queen.
Both the queen and the male come from colonies that are particularly good at killing mites by chewing off their legs.
It’s a grisly end for these tormentors and – just maybe – a fair shake for the honeybees.
Hey sugar, what’s shakin’? We’ve got more bee stories for you. Bindweed turret bees fill their underground nests with pollen. See those “pollen pants”? But freeloading flies drop their own eggs into the nests … from the air!
Also, PBS Digital Studios wants to know what you enjoy on YouTube and what you want more of. Follow the link in the description to take their annual survey. You even get to vote on new show ideas. Thanks for representing, and please tell them Deep Look sent you.