This Fly Torpedoes a Bindweed Bee’s Nest

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A “bee fly” looks a bit like a bee, but it’s a freeloader that takes advantage of a bindweed turret bee’s hard work. The bees dig underground nests and fill them with pollen they collect in the form of stylish “pollen pants.” As the bees are toiling on their nests, the flies drop their *own* eggs into them from the air. But the bees employ a tricky defense against the flies.


Life for bindweed turret bees is violent and unfair.

It’s spring in California, and these male bees are in an all-out brawl, desperate to mate with the female trapped at the bottom of this pile.

Sometimes the fight is so intense that the female they’re going after gets crushed to death.

But if she survives, she and the winner steal away and mate … until another male wants in. Buzz kill!


Now she starts an epic dig, prepping a place to lay her eggs underground.

She tirelessly scoops earth with her mandibles, dousing it with nectar she collected earlier to soften it.

The majority of the world’s bee species – 70% – nest in the ground. These ones chose a dirt parking lot. Some nice folks cordoned it off to protect the bees.

Females work side by side. Each is “queen” of her own funky little castle.

They build turrets, but only some of them are vertical.

Many are tunnel-like, with a sideways entrance.

Others curve down.

You’ll see why that’s important in a bit.

Once the bees are done digging, they head off on another mission. They gather pollen from one plant only: morning glories, also known as bindweeds.

She rubs her shaggy legs all over that pollen.

And down she goes with her haul.

Pollen pants!

Inside her nest, she packs the pollen into neat balls – each one in its own chamber – and lays an egg on top.

When the egg hatches into a larva, it will live off the pollen.

As she toils, freeloaders show up.

They look like a bee, but their huge eyes give them away.

They’re called … wait for it … bee flies.

The fly doesn’t dig or gather pollen for her young. She just hovers over a bee’s nest and … yup, she’s dropping her own eggs in there.

She’ll drop 200 eggs over her lifetime.

This is where those tunnels and curved turrets are useful. They make it harder for the flies to drop their eggs in from the air.

But when the fly does succeed, the fly’s egg hatches into a larva that digs tiny hooks into the bee larva.

As the bee eats the pollen and grows, the fly larva sucks it dry.

Sometimes the flies are so successful, they can nearly wipe out a population of bees.

But these bees don’t give up. Two or three months of mating, foraging and warding off parasites come to an end when they seal up their nests with dirt.

Below ground, babies will grow.

The following spring, if the bees are lucky, a new tiny city will burst to life, full of bees persevering just as their mothers did before them.

Let’s talk about yellowjackets. It’s true: These ladies have a special taste for flesh. But they don’t eat it themselves. They bring it to their young. How? By crashing your cookout and carving your burgers and dogs into teeny-tiny meatballs. Enjoy!