Orb-weaving spiders outsource their hearing to their web

By Patience Asanga

Image source: Binghamton.edu. Credit: Jonathan Cohen 

Determined not to let their size put them down, many small animals have devised means to carry on with their lives like every other large animal. We've heard of how ants carry heavy loads with the help of their neck joints that can withstand pressures up to 5000 times the ant’s weight. 

Today the spotlight is on spiders. A new study finds that these guys have refused to allow their body size to constrain their sense of hearing, as with other small animals that do not have enough room for an eardrum. The study says these little weavers found a way to outsource their hearing to their web, which is entirely different from how the auditory organs of small animals operate. 

Following several scientific experiments on bridge spiders (Larinioides sclopetarius), Jian et al. (2022) found that this spider uses its orb-web to capture sound. 

Jian and his team collected female bridge spiders from their natural habits and placed them inside wooden frames in an anechoic chamber. They allowed each spider to weave orb-webs in their new environment and then settle down before experimenting on them. 

The team stimulated the spiders with sounds from different speakers — a subwoofer, a tweeter, a loudspeaker, and a mini-speaker. Upon stimulation, the spiders responded by crouching, stretching out, raising their forelegs into the air, and turning. 

Previous studies proved that even though spiders do not have ears as vertebrates do, they can still hear sounds with the help of the tiny hairs on their legs. Jian and colleagues’ experiment has added to this knowledge. They believe that bridge spiders convert their orb web into an external ‘eardrum,’ which enables them to detect and localise distant airborne sounds by picking up motions on their web threads. 

Also, by outsourcing their hearing to their webs, bridge spiders extend their sound-sensitive surface up to 10,000 times their body size, the authors wrote. 

‘The spider is really a natural demonstration that this is a viable way to sense sound using viscous forces in the air on thin fibres. If it works in nature, maybe we should have a closer look at it,’ says Professor Ron Miles, one of the paper's authors. 

The researchers hope that this discovery will someday help them to design ‘extremely sensitive bio-inspired microphones for use in hearing aids and cell phones.’