Dragonflies 'Invisible To Their Victims'

Ananova ^ | 6-4-2003

[blam]

Dragonflies 'invisible to their victims'

Researchers have found dragonflies know how to make themselves invisible to airborne prey and territorial rivals.

They make themselves invisible by using a system even more sophisticated than the radar avoiding technology of America's stealth aircraft.

Using ultra-precise positional sensing and flight control, a dragonfly can move in such a way that it appears to an enemy to be a stationary object blending into the background.

The "motion camouflage" technique allows the creature to stalk its victim undetected.

Scientists in Australia made the discovery after using stereo cameras to record territorial air battles between rival male dragonflies.

By studying the insects in three dimensions, the researchers established how motion camouflage works.

They described how an attacking dragonfly adjusts its position so that its image always occupies the same spot on the target's retina. Camouflaged against the background, the dragonfly becomes invisible even though it is moving.

The scientists, led by Akiko Mizutani, from the Australian National University in Canberra, wrote in the journal Nature: "Deployment of this sophisticated technique by the oldest airborne predator tricks the victim's retina into perceiving the stalker as stationary even while it darts about in pursuit."

The researchers reconstructed 15 three-dimensional dragonfly flight trajectories, six of which showed clear evidence of motion camouflage.

In many cases, the pursuing dragonfly flew away from its rival rather than towards it in order to maintain the disguise. Sometimes a dragonfly would imitate near and far fixed objects during a single pursuit, showing it could combine different types of motion camouflage.

Story filed: 18:05 Wednesday 4th June 2003

[Arkie2]

That explains why I run into that pole in the parking lot after 5 adult refreshments! It's camouflaged because it keeps moving. I know it's true because I see it move!

[RightWhale]

the oldest airborne predator tricks the victim's retina into perceiving the stalker as stationary even while it darts about in pursuit."

Mosquitos and flies get about a month headstart, then the dragonflies emerge, small creatures to begin with. As the summer goes on, the dragonflies get bigger and the mosquitos and flies tend to disappear. It's true, dragonflies circle their prey and then swoop straight in. Dragonflies don't see well, though, they check in on any small dark spot on a treebranch.

[Solamente]

So - the dragonfly is cognizant of the sweet spot in its victim's retina, randomly and on the fly?

[NerdDad]

This never worked against my dad. He always took his .22 when we went dove hunting in West Texas. If anyone came up and wanted to hunt with us, he would sit at the edge of the pond and shoot the dragonflies with the .22 as way of intimidating the other hunters into leaving.

[joesnuffy]

they are nice bugs
they eat skeeters like there is no tomorrow

[joesnuffy]

Im looking for a large beer stein
with a dragon fly emboldened upon it
So that I can declare

My dragon fly
flagon dry

[headsonpikes]

Now that's astounding!

[martin_fierro]

A hunting dragonfly in action.

[Mark was here]

[Renegade]

The flies and mosquitos had a year head start. The dragonfly nymph lives for a full year underwater as a predator with an "alien" like jutting jaw . It emerges and undergoes metamorphisis the second year.

[ricpic]

"The researchers reconstructured fifteen three- dimensional dragonfly flight trajectories, six of which showed clear evidence of motion camouflage."

Nine drag-ass dragonflies. Flight school drop-outs. Their families disgraced.

[VOA]

cool!

[Renegade]

They were a Romulan breed of dragonfly.( "The 6") The genes for " cloaking" were embedded in their DNA.

[Junior]

How cool is this?!

[Junior]

When he said "oldest" I think he meant history-wise. Dragonflies have been around since at least the Carboniferous.