Why Is a Praying Mantis Wearing 3D Glasses?

Imagine a scenario where you are reading notes in a laboratory research notebook. Now, imagine that the scenario in the notebook involves forcing an insect to hang upside down, but the insect isn’t just hanging upside down. It’s hanging upside down while watching a 3D movie, and wearing 3D glasses. It sounds like something out of a bizarre science fiction novel instead of a professional notebook. As an authentic study, it has a lot of value to add to the scientific community.

Insect Vision

Humans have forward-facing eyes and stereopsis. That means that both of the eyes can come together to create one 3D image through the brain. Insects don’t have forward facing eyes, and they didn’t evolve along the same lines as humans. Therefore, it was concluded they didn’t have stereopsis. Because they hunt live prey, scientists often wondered how they survived without 3D vision.

To understand how 3D vision affects your life, compare two viewing scenarios. If a box was sitting in your living room, and the open end faced you, you would jump when something in the box leapt toward you, because 3D vision allows you to perceive that something is coming in your direction. Now, consider the scenario using a television rather than a box. If something leaps toward you on the television, there is no depth to it, so you don’t perceive it as a threat. This is called 2D vision. 3D vision helps living beings understand the distance between them and something or someone else. It’s a survival trait in more ways than one, and it is becoming clear that insects may also have this trait.

Movies for the Praying Mantis

Recently, Jennifer Ready designed and built a theater for a praying mantis. The theater used 3D imaging. The mantis, whose hunting position involves being suspended upside down, was affixed with 3D “glasses” in the way of two different-colored lenses. Only, unlike humans, the mantis doesn’t perceive the color red very well, so red was replaced with green. The movie may as well have been titled “Attack of the Flying Discs,” because it involved small discs that looked as if they were flying. Their flight pattern was designed to be similar to that of the prey the mantis usually seeks out.

The climax of the movie occurred when the disc appeared to be within 2 cm of the face of the mantis. This is the range at which the mantis strikes out for its prey. The scientists were not disappointed. The mantis did strike out and was most likely confused as to why it captured exactly nothing. The harmless disc continued its flight across the computer screen that the mantis was viewing.

What exactly can be learned from this? In all seriousness, it changes the way scientists understand the perception of insects. For the average person, the notes in this scientific notebook mean that red is probably the best color to use when you are trying to sneak up on a praying mantis.