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How Hoverflies Spawn Maggots that Sweeten Your Oranges

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Oblique streaktail hoverflies zip from bloom to bloom wearing a wasp costume to avoid getting eaten. But it’s all show – they don’t even have stingers! Their fierce maggots, on the other hand, devour hundreds of insect pests. As they gorge, they help keep orange trees safe from disease.


What hovers like a tiny helicopter and flies backwards?

Has the flashy backside of a wasp … the huge eyes of a fly … and spawns murderous maggots?

Meet the hoverflies, also known as “flower flies,” or syrphids.

There are 6,000 species, each with its own style.


Bold stripes or plump fuzzy bodies make them look like wasps or bees. But it’s just a ruse. This protective disguise tricks predators into thinking they might get a face full of stinger if they try to eat the hoverflies. This bluff is called Batesian mimicry.

This one with the intricate pattern on her back is an oblique streaktail. Right now, she’s on a mission in this Southern California flower patch, fueling up on the pollen that will help her grow her eggs.

She loves this fragrant alyssum and pollinates it as she darts from bloom to bloom. See how precisely she lands?

Her wraparound eyes catch the faintest motion … just in time for her to escape this hungry crab spider.

After filling up on pollen, she uses her stubby, but powerful, antennae to smell for the perfect spot for her eggs … an orange tree under attack by these yellow insects with curlicue poop: Asian citrus psyllids.

The hoverfly lays her eggs next to them. When maggots hatch out of the eggs, they’ll have plenty of those psyllids nearby to eat.

Orange growers despise Asian citrus psyllids, which spread a destructive bacterium.

Instead of these juicy beauties, trees suffering from this “citrus greening” make green, bitter fruit … and eventually die.

So, scientist Nic Irvin, at the University of California, Riverside, has planted alyssum in orange groves to attract oblique streaktails.

Their maggots hunt for psyllids on the orange trees.

But the psyllids have a security detail: Argentine ants.

They feed on the psyllids’ poop.

In exchange, the ants try to keep the maggots away.

But this big one has the upper hand.

It digs its mouthparts in and injects some venom. It even sucks out a little taste, to see if it might want to eat the ant. Nope. It’s really after the psyllids.

Each maggot will devour more than 400 in the week before it turns into a pupa.

And that gluttony means more oranges for you and me.

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