Praying mantises do not see the world like humans do. Scientists at the University of Newcastle in Britain discovered that mantises have devised a unique way to see in three dimensions. This previously unknown type of vision is based on motion over time and not image comparison. The study was published in the journal Current Biology and funded by the Leverhulme Trust.
Previous research suggested that praying mantises use 3-D vision, also called stereopsis. Stereo vision lets the slightly different views of each eye combine to work out how far away things are. Stereoscopic vision is present in most mammal species except whales and dolphins, is comparatively rare in birds, and is virtually unknown in the insect world. In fact, mantises are the only insect known to use 3-D vision.
Stereoscopic vision in praying mantises works in a significantly different way to that found in mammals such as humans. Human brains need to meld two static images from each eye to form a coherent picture. Humans are incredibly good at seeing 3D in still images.
Mantises have a unique sort of vision. Mantis vision depends on identifying which bits of a visual field are moving. Mantises can see depth if there’s a moving object. While what they see is blurrier, they process the image more quickly and are hyper-focused on things only an inch or two away. This type of vision does not exist in any other known creature.
The team at Newcastle University tested the insects’ vision by training a mantis to wear a pair of tinted glasses affixed with beeswax and watch movies. The lenses had one blue filter paired with one green filter. Using the color filters, the scientists could project a different image to each eye. When combined, the images created an illusion of depth. The mantis was evidently fooled by the illusion and tried to catch a target dot that moved against a polka-dot background.
The scientists then manipulated the target dots in ways a person would not be able to detect. Dots that began in the same place but moved up in the right image but down in the left also provoked mantis strikes. Praying mantises are ambush hunters, striking at movement that catches their attention. Their brains appear to ignore the portion of the world that is static and hyper focus on anything that is moving.
The scientists say they hope to apply this visionary technique to robots. Current attempts to develop stereoscopic vision in mobile robots are all modeled on the system used by the human brain. The scientists are now working to create a computer algorithm that replicates mantis sight.