Ogre-Faced, Net-Casting Spiders Use Auditory Cues to Detect Airborne Prey

Area of Science:

• Arachnology
• Animal Behavior
• Sensory Biology

Background:

• Spiders exhibit diverse prey capture strategies, from web entrapment to active pursuit.
• Ogre-faced net-casting spiders (Deinopidae: Deinopis) use a unique net-casting technique suspended in a frame web.
• Previous research suggested acoustic detection might play a role in their 'backward strike' hunting method.

Purpose of the Study:

• To investigate the auditory capabilities of Deinopis spinosa for prey detection.
• To determine if acoustic stimuli can trigger the backward strike behavior in these spiders.
• To explore the functional significance of auditory sensitivity in their predatory and anti-predator behaviors.

Main Methods:

• Behavioral assays were conducted to assess responses to acoustic stimulation at varying distances and sound pressure levels (SPL).
• Neurophysiological recordings were performed on brain and foreleg tissues to map auditory sensitivity across different frequencies.
• Specific sound frequencies mimicking insect flight tones and higher frequencies were used to elicit predatory or anti-predator responses.

Main Results:

• Deinopis spinosa can detect auditory stimuli from up to 2 meters away, at or above 60 dB SPL.
• Acoustic sensitivity spans a broad range (100–10,000 Hz), with backward strike behavior triggered by frequencies matching prey flight tones.
• Higher frequency sounds, potentially from avian predators, did not elicit predatory responses, suggesting a role in anti-predator detection.

Conclusions:

• Auditory cues are sufficient to trigger the backward strike hunting behavior in Deinopis spinosa.
• The spider's auditory system is tuned to frequencies relevant for detecting prey, demonstrating specialized sensory adaptations.
• Differential responses to sound frequencies suggest a dual role for hearing in both predation and predator avoidance.