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United States Department of Agriculture

Agricultural Research Service

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New fly in town...

Flying bugs that make pests of themselves in North American greenhouses had better watch their backs.

The Flash video shows a hunter fly. It is still, but its wings are trembling.The Old World hunter fly is a predatory insect. Dr. Watts says, "Watch out pests!"

That's because there's a new fly in town, and it's out to chase these bad bugs down and EAT them! This new fly even has a scary name: the Old World hunter fly. Its scientific name is Coenosia attenuata.

Scientists in New York State with Cornell University and the Agricultural Research Service (ARS) recently made the first-ever identification in North America of this winged predator.

The hunter fly was first described in southern Europe more than 100 years ago. In Europe, it has an even more awesome name: “The killer fly!”

The hunter fly is from the same insect family as—and looks just like—the common house fly you may see buzzing in and out of your home, except that the hunter fly is only about half the size of a typical house fly. But what makes Old World hunter flies really cool is that they seem to enjoy a challenge.

They just sit there and wait—and spring into action only when another bug flies by.That's right; they only chase a prey that is in flight! If an insect is not flying, they won’t attack it, even if it’s close by, says Steve Wraight.

He’s an ecologist in the ARS Plant Protection Research Unit at Ithaca, New York, who helped identify the fly here.

Pint-sized predator

Wraight says that the flies catch their targets, stab them through the neck with a part of their mouths that looks like a dagger, and then suck up their victim’s squishy guts. How yummy!

A hunter fly devours an insect. Old World hunter flies only chase prey in flight.
Half the size of a typical house fly, Old World hunter flies have a full appetite! Here, the predatory insect devours its prey. Photo courtesy of Todd A. Ugine.

Not only that, but the hunter fly’s larvae—the immature form that hatch from eggs—are also predatory, feeding mainly on the larvae of other insects, including fungus gnats. You can see why many bugs would really hate having this hunting fly around!

But scientists think that many people who grow plants in greenhouses will love the hunter fly. That's because it likes to eat some of the insects that greenhouse keepers hate the most. These include pains-in-the-neck such as fungus gnats, shore flies, leafminer flies, fruit flies, moth flies and some leafhoppers.

In fact, Wraight says that Old World hunter flies may one day be raised and sold to keep insect pests out of greenhouses.

Wraight says that hunter flies seem to have been on the move for a long time: "From their original home range in Europe, they have spread to southern Asia, Africa, the Canary Islands, New Guinea, and Australia, and they were also found in South America before being discovered here."

Scientists aren’t sure exactly how the hunter flies got here. Maybe they made the trip in soil and plant material shipped here as part of the horticulture trade. Horticulture is the science and art of growing fruits, vegetables, flowers or ornamental plants, and thousands of tons of these products are shipped from country to country each week.

The flies were first noticed in 1999 in Onondaga County, New York. They were then studied by entomologists at Cornell University with help from Wraight. Since then, they've also been identified in many other states and also in several provinces of Canada.

So there you have it, flying greenhouse pests: Consider yourselves warned. Beware because the hunter fly is out to get you!

—By Luis Pons, Agricultural Research Service, Information Staff.

Dr. Watts: Inside a greenhouse are two benches, each holding potted plants of different sizes and shapes. A hunter fly sits outside the greenhouse, on the path. He is much larger than a greenfly would be in real life. A pest—also much larger than in real life—floats lazily towards the greenhouse, but as it nears the entrance, the hunter fly pounces! The hunter fly stabs the pest with part of his mouth and devours it. The greenhouse plants are safe, and the hunter fly is full. Like a watchdog, a hunter fly can keep invaders out! Here, a hunter fly attacks and eats a pest before it enters my greenhouse! ( Of course, real insects are much, much smaller.) Notice how the hunter fly first stabs the insect, then devours it. (Rollover the image of Dr. Watts for a description of the video.)

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Last Modified: 8/12/2016
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