A Binghamton University study shows orb weaver spiders respond to sound vibrations in their web, possibly using them to hear.
For much of his career, Ron Miles, a distinguished professor of mechanical engineering at Thomas J. Watson College of Engineering and Applied Science, has been researching insects’ responses to acoustic vibrations. His goal is to understand how an insect’s compact hearing system works in order to develop more advanced microphone technologies. Miles mostly works on advancing medical instruments, such as hearing aids.
For this study, Miles worked alongside Ronald Hoy, a biology professor in the department of neurobiology and behavior at Cornell University, Carol Miles, an associate professor of biology at BU, and two Ph.D. candidates being advised by Miles. In 2017, the group published an article, “Outsourced Hearing in an Orb-Weaving Spider That Uses Its Web as an Auditory Sensor,” based on their study of orb-weaving spiders.
During a routine stroll through the BU Nature Preserve, Miles’ former student, Jian Zhou, ‘18, a postdoctoral appointee at Argonne National Laboratory, noticed an orb-weaver spider in its web, swaying in the wind. Taking notice of the spider’s unique movements, Zhou had wondered if it was responsive to sound stimuli. He then collected the spider, along with some of its web, and brought it back to Miles’ laboratory.
“We were looking for materials and ways to study,” Miles said. “[Zhou] was hiking in the Nature Preserve and he noticed that spider webs would blow in the wind. He thought maybe spider silk would be a good material since it is strong.”
To test the spider’s responsiveness, Miles and Zhou placed the spider in the anechoic chamber in Miles’ lab. According to Hoy, the soundproof room is one of the largest in the United States, and its structure and position on top of springs makes it highly effective in absorbing sound waves.
With the help of a new team member, Junpeng Lai, a Ph.D. candidate studying mechanical engineering who is advised by Miles, the group directed sound vibrations of various decibels toward the web at over 1,000 angles. Using a laser vibrometer, the team was able to measure the vibration patterns. Hoy said the equipment in the lab accurately captured each vibration, which allowed the spider’s responses to be studied.
“Miles’ lab has wonderfully sensitive instruments — like laser vibrometers and force transducers — to study the mechanical response of insect and spider acoustic organs or flow sensors in general,” Hoy wrote in an email. “We are neurophysiologists and behavioral biologists so we’re interested in how the brain processes acoustic signals during behavioral activity.”
The team determined that the spider both responded to each sound and was able to locate where the sound was coming from. The spider’s accurate response to sound waves in its web gave Lai the idea that the spider could possibly use its web to hear.
“It changes how people see spiders,” Lai said. “We just see the web as a capturing-prey tool — now it serves as an ear for spiders.”
Miles agreed and said many animals and insects hear through many small hairs rather than eardrums.
“Most animals don’t have eardrums,” Miles said. “Most animals, if they can hear, tend to use little hairs. This is also true in insects. They are covered in hairs, a lot of the time those hairs detect sound.”
According to Hoy, advances in microphone technology can be discovered through the study of insects’ hearing systems. Hoy said the project is important because it proves that the creation of miniature synthetic sound receivers is possible.
“The animals (insects and spiders) are quite small, even tiny, in the first place, so their hearing organs are even tinier — meaning that they have solved the problem of miniaturization for vision and hearing,” Hoy wrote in an email. “Hearing at microscale (even nanoscale) is of great interest to biologists as well as engineers, for whom miniaturization is an essential design feature for applications that have relevance to human performance.”
Ben Talbot, a sophomore majoring in mechanical engineering, said the research made him feel enthusiastic about being a BU student.
“It’s very cool,” Talbot said. “I think it’s interesting that something like that is happening here at the University. You hear of stuff like that, but never close to home.”
Although the team did years of work on the spider acoustics project, their research is not over. The team was able to show evidence that spiders are responsive to sound vibrations, but are not positive about the purpose of the response. Lai implored the biology department to continue researching the topic.
“Does the spider use it to hunt or escape from predators?” Lai said. “That is for biology students to answer.”