Recent studies involving 3-D glasses reveal a perhaps surprising truth: praying mantises have depth perception.
Jenny Read, a researcher at Newcastle University in the U.K., conducted an experiment to test the sight of praying mantises. First, she made little 3-D glasses similar to old school 3-D movie glasses. Next, she pasted these glasses to the mantises' foreheads with some beeswax. Finally, she suspended the mantises upside down—which is their preferred hunting position—and in front of a computer screen that displayed a series of moving disks resembling mantis' prey. If the mantises were able to see in 3-D, they would only attack the virtual prey when they appeared to be about two centimeters away. And this is exactly what Read observed.
Judging distance is crucial for insects. When an insect has an almost instant and accurate interpretation of distance, it can do a lot more than it could without 3-D vision. When hunting, for example, an insect needs to know how far away its prey is if it has any chance of catching it. Also, if the insect is trying to escape from a predator, it needs to know how far away shelter or safety is.
While Read's is an interesting study, there is still much research to be done on the topic. Read doesn't know how the 3-D vision of praying mantises works, but she is determined to find out. It's hard to answer this question because praying mantises' eyes are on the sides of their heads rather than forward facing. Also, insects evolved the ability to see in 3-D independently of other animals, so scientists aren’t sure if their sight works the same way. Read hopes to continue her studies and have additional answers soon.