The ogre spider does not have ears. On the other hand, it is able to hear its prey and its possible predators at least two meters away. A recent study tried to provide an explanation for this astonishing phenomenon. Learn the interesting spider facts here.
Sensitive to low frequencies
Spiders in the Deinopidae (or ogre spider) family are named after their appearance. Indeed, these have huge protruding eyes and middle of the head. If these eyes give these spiders good night vision, their main characteristic is quite different. The deinopidae can hear their prey and their predators at a distance of two meters. However, these spiders have no ears. A study published in the journal Current Biology on October 29, 2020, focused on Deinopidae .
According to researchers at Cornell University (United States), these spiders can like others to feel the vibrations agitating their web. However, they can also feel the vibrations in the air, unheard of. This is possible thanks to dedicated receivers, instead of ears. Indeed, these spiders carry bristles (trichobothria) making them sensitive to the acoustic stimulus, and therefore able to capture low frequencies. They are also endowed with sensilla, that is to say, small structures located on the cuticle housing the sensory neurons.
A fascinating hunting technique
“These spiders have finely tuned sensory systems and a fascinating hunting strategy. It’s totally unique. These spiders have huge eyes so they can see at night and catch things on the ground, but they can hear quite well, picking up sound through their metatarsal organ, as these spiders are good at capturing things from the air, ” said Jay Stafstorm, lead author of the study ina statement.
Motionless most of the time, the Deinopidae let themselves descend to the ground in order to weave a web serving as a fishing net. The goal? Catch flying insects. When a noise approaches, the spiders perform a sort of backflip to capture their prey in the web. However, this act results not from vision but from hearing.
The researchers subjected several spiders to different frequencies while tracking their neuronal activity using electrodes on their brains and legs. Thus, spiders react to stimuli ranging from 100 to 1000 Hz. This auditory sensitivity triggers their hunting behavior. The next step for the researchers will be to understand whether the Deinopidae are able to identify the origin of sound in space.