Ogre-Faced Spiders Can 'Hear' Without Ears, Study Says

Deinopis Spinosa uses a precise method to detects its preys, it seems.
Chris Young

Now that we're so close to Halloween, what better time to get news about some of the word's creepiest-looking spiders?

The ogre-faced spider, or Deinopis Spinosa, has long been known to be able to capture insects flying out of their field of vision with immense precision. Scientists at Cornell University have now confirmed how this is possible.


Ogre-faced spiders have metatarsal sensitivity

In a new study, researchers confirmed that ogre-faced spider uses fine-tuned metatarsal sensitivity — sensors at the tip of its legs — to detect sounds of various frequencies from up to 6 feet away.

The spider reacts to specific sound cues that it knows to be made by airborne insects, triggering a backflip that launches its body straight into its prey.

"These spiders have finely tuned sensory systems and a fascinating hunting strategy," lead author Jay Stafstrom, a postdoctoral researcher in the laboratory of Ronald Hoy, professor of neurobiology and behavior at Cornell, explained in a Cornell University press release.

"These spiders have massive eyes so they can see at night and catch things off the ground, but they can 'hear' quite well, detecting sounds through their metatarsal organ, as these spiders excel at catching things from the air," he continued.

Ogre-Faced Spiders Can 'Hear' Without Ears, Study Says
Deinopis Spinosa spinning its web.              Source: Jay Stafstrom/Cornell University

Recording neural activity in spiders' legs

Ogre-faced spiders are mainly found in the southeastern United States. Strangely, despite their impressive ability to pick up sound waves due to the metatarsal organ located on their legs, the spiders don't actually have ears.

In order to ascertain the origin of the spiders' ability to precisely catch its prey, even when not in its field of vision, Stafstrom brought a few of the spiders to Gil Menda, a postdoctoral researcher in Hoy's lab.

Menda recorded the neural activity from the brains and legs of the spiders. When he played pure-tone frequencies to the spiders, the researchers noted the spider's neurons reacting to different tones.

"While the spiders were sensitive to low-frequency tones, as expected, we didn't really expect to see net-casting spiders sensitive to a wide range of frequencies - all the way to 10 kilohertz," Stafstrom said.

The thought of specific sounds triggering a ninja-like backflip from a spider that looks like a face-hugger from the movie "Alien" definitely gets us in the spirit of Halloween.