Praying mantises at Newcastle University in the U.K. have been outfitted with tiny 3D glasses and treated to special screenings as part of an experiment that researchers hope will inform our understanding of 3D vision in humans and possibly even robots.
“No one’s put 3D glasses on an insect before,” says Jenny Read, the study leader and a professor of vision science at the university, on the phone from Newcastle.
Scientists have already demonstrated that praying mantises have 3D vision, but no one has studied how it works, Read notes.
In the recent experiment, the mantises hung upside down in front of a computer screen wearing the glasses while a 3D image was projected just out of their reach.
“It’s not exactly Star Wars, but it fools them into thinking there’s a little bug,” she says.
Under observation, the tiny predators reached out and tried to grab the silver-screen prey. That reaction confirmed they can see in 3D and proves the 3D glasses work, Read says.
“They see in the 3D all the time, but in order to investigate it, we need to be able to manipulate it.”
To get the insects to co-operate, the team put the mantises in a freezer for a couple of minutes so they wouldn’t protest when miniature coloured filters were “popped on” their faces with a blob of beeswax.
Though the glasses may look ungainly, the insects don’t seem to mind them much.
“They wear them in their cages,” Read says. “They still hunt and catch their crickets just as normal.”
The team’s results were recently published in the journal Scientific Reports.
They hope future experiments will shed some light on exactly how the mantises’ vision works.
Read sees two “broad possibilities.” One, insect vision works the same as human 3D vision, in which case studying the insects can help scientists understand human vision. Two, the insects have evolved a completely different solution.
Even if insect 3D vision proves to be different from that of humans, Read believes the experiments still have practical applications for robots and possibly even drones.
“Currently, most machine 3D vision is sort of based on human 3D because that’s what we know,” she says.
“If insects have come up with something different, one assumes that it’s kind of simpler and cheaper, because they’re so tiny and so low-power.
“This is just a starting point, really.”
Praying mantises are the only known invertebrates to have 3D vision, or stereopsis, as it’s known in the scientific community, Read says.
Invertebrates are a group of animals that do not have backbones; the category includes everything from tarantulas to giant squid.
The mantises’ ability to perceive depth may have had an evolutionary function, enabling them to spot their prey even when it’s camouflaged, Read says.
“They’ll ambush predators. They spend a lot of time hanging upside down, waiting for something to come within range, and if it does, they reach out really quickly … and try to grab it.
“You kind of get one shot at that. If the insect’s out of range and you strike at it, you’ve kind of given yourself away.”