World’s tiniest 3D glasses reveal how praying mantises see the world

Praying mantises are the only invertebrates known to see in 3D. The predatory insects excel at detecting prey that comes within striking distance, but—unlike us—their depth perception only works when the prey is moving. How do we know this? In a new study, scientists glued the world’s tiniest 3D glasses on 20 praying mantises (Sphodromantis lineola) and showed them a series of movies depicting patches of moving dots—potential “prey items”—camouflaged against a matching background. The insects tried to catch “prey” that appeared to be within 2.5 centimeters of their perch. And they could still do it even when the “prey” item—or dot configuration—looked completely different to the two eyes, something that people found challenging when they were asked to perform the same task, the team reports today in Current Biology . Humans see in 3D by stitching together the actual image coming in from one eye versus the other, but this work shows that praying mantises only bother stitching together the motion—the actual image doesn’t matter to them. It’s the first time this kind of 3D vision has been found in nature, and it’s yet another example of evolution coming up with different solutions to the same problem—in this case, when to strike at a passing fly.