Praying mantises with tiny 3D glasses have stereo vision

Praying mantises sporting tiny 3D glasses that were held in place with beeswax have revealed a new kind of ‘stereo’ vision that may help improve robot sight.

With two teardrop-shaped, light-filtering lenses perched on their heads, the insects lashed out at images of tempting prey in a special 3D film, a team of scientists said. 

Currently robot algorithms for sight require a lot of computing power. 

However, if scientists could replicate the way mantis sight detects depth they could create more lightweight robots with better 3D vision. 

 

Praying mantises sporting tiny 3D glasses that were held in place with beeswax have revealed a new kind of ‘stereo’ vision that may help improve robot sight

Also known as stereopsis, 3D or stereo vision helps humans and other creatures determine the distances to objects we see. 

Scientists then observed the insects’ reaction to more complex images, and learnt that mantis vision works very differently to ours. 

‘Mantises only attack moving prey, so their 3D doesn’t need to work in still images,’ said Vivek Nityananda of Newcastle University, one of the authors of a study published in the journal Current Biology.

‘We found mantises don’t bother about the details of the picture, but just look for places where the picture is changing,’ he said in a video explaining the experiment.

This was the case even when each eye looked at two completely different images – an ability humans don’t share.

According to fellow researcher Jenny Read, this was a simpler method of 3D vision, and could have implications for building lighter machines, such as drones.

‘Current machine stereo algorithms require a lot of computing power,’ she said.

With two teardrop-shaped, light-filtering lenses perched on their heads, the insects lashed out at images of tempting prey in a special 3D film, a team of scientists said

With two teardrop-shaped, light-filtering lenses perched on their heads, the insects lashed out at images of tempting prey in a special 3D film, a team of scientists said

Scientists then observed the insects' reaction to more complex images, and learnt that mantis vision works very differently to ours

Scientists then observed the insects’ reaction to more complex images, and learnt that mantis vision works very differently to ours

‘Reducing the amount of computer power necessary means smaller, lightweight robots could use mantis stereo algorithms to detect depth.’  

Each eye sees an object at a slightly different angle, but the brain merges the two images together and uses the difference to calculate how far something is.

Other animals with this ability include monkeys, cats, horses, owls and toads, said the research team.

According to fellow researcher Jenny Read, this was a simpler method of 3D vision, and could have implications for building lighter machines, such as drones

According to fellow researcher Jenny Read, this was a simpler method of 3D vision, and could have implications for building lighter machines, such as drones

WHAT ARE PRAYING MANTISES AND HOW DO THEY SEE?

There are over 2,400 species of mantises in 15 families, which live in temperate and tropical habitats around the world.

Their closest relatives are termites and cockroaches.

Mantises may have a visual range of up to 20 metres. Their compound eyes may comprise up to 10,000 ommatidia – clusters of photoreceptor cells. 

Mantises have two grasping, spiked forelegs or raptorial legs in which prey items are caught and held securely.

Most mantises are exclusively predatory. 

They eat small insects or their siblings when young and when they grow larger, have been known to prey on small scorpions, lizards, frogs, birds, snakes, fish, and even rodents.

The eyes are widely spaced, affording a wide binocular field of vision and at close range, precise stereoscopic vision.

The dark spot on each eye is a pseudopupil. As their hunting relies heavily on vision, mantises are primarily active during the day.

It is possible that 3D vision in mantises is closer to that of vertebrates, where disparities between the positions of an object’s image in the two eyes can be detected and used to reveal the object’s position, even when the object is camouflaged and is invisible in either eye individually.

If this is the case, it would mean that mantises have independently evolved similar 3D processing to vertebrates.

The mantis is the only insect known to have stereo vision, but given its tiny brain, scientists have long suspected it must involve a simpler process.

The eyes are widely spaced, affording a wide binocular field of vision and at close range, precise stereoscopic vision.

The dark spot on each eye is a pseudopupil. As their hunting relies heavily on vision, mantises are primarily active during the day.

To test this, the team created special, tiny 3-D glasses out of blue and green-coloured filters, and used beeswax to fit them to 10 adult insects.

The experiment revealed that mantis stereopsis ‘uses a fundamentally different computational algorithm’, they said.

‘Thus, while there is no evidence that mantis stereopsis works at all with static images, it successfully reveals the distance to a moving target.’

 



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