Ogre-faced spiders can hear despite having no ears

Ogre-faced spiders hide during the day and hunt by night, going from Florida palm fronds and making silk nets on insects on the ground and in the air. They are named after their massive eyes. Having an incredible night vision, these spiders can hear their predators and prey.

These spiders use their hair and joint receptors on their legs to pick up sounds from the environment from at least 2 meters away because they have no ears. Spiders can hear low-frequency sounds from insect prey as well as higher frequency sounds from bird predators.

“I think many spiders can actually hear, but everybody takes it for granted that spiders have a sticky web to catch prey, so they’re only good at detecting close vibrations,” says senior author Ron Hoy, professor of neurobiology and behavior at Cornell University. “Vibration detection works for sensing shaking of the web or ground, but detecting those airborne disturbances at a distance is the province of hearing, which is what we do and what spiders do too, but they do it with specialized receptors, not eardrums.”

Ogre-faced spiders use their webs as a weapon instead of passively waiting for prey to fall into a web and get stuck.

After spending the daylight hours camouflaged, they emerge at night to dangle close to the ground and cast their webs like a net on unwary insects. They use their keen night vision to catch the prey on the ground, and can also catch insects in the air by performing a backwards strike, for which they don’t rely on vision.

“In a previous study, I actually put dental silicone over their eyes so they couldn’t see,” says first author Jay Stafstrom, a postdoctoral researcher in the Hoy Lab. “And I found that when I put them back out into nature, they couldn’t catch prey from off the ground, but they could still catch insects from out of the air. So I was pretty sure these spiders were using a different sensory system to hunt flying insects.”

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