• Moth found to have ultrasonic hearing

    Ohio State University

    The phases of a greater wax moth.

    By Tia Ghose
    LiveScience

    The ubiquitous greater wax moth is ordinary in every way but one: It has the ability to hear the highest-known sound frequency.

    The greater wax moth's hearing goes up to about 300 kilohertz, nearly 100 kHz higher than the hearing of some bats.

    "This is the animal with the highest frequency sensitivity yet recorded, there's no other animal that can hear such a high frequency," said study co-author James Windmill, a bioacoustician at the University of Strathclyde in Scotland.

    The moth's ultrasonic hearing range, which was described Tuesday in the journal Biology Letters, could help the creature hear the sonar communication of their predators, bats, Windmill said. [Flying Mammals: Gallery of Amazing Bats]

    Humble moth
    The nondescript brown moth species, Galleria mellonella, lives in North America, Europe and Asia and has a 1.1-inch (3-centimeter) wingspan. Its tiny ear is just 0.02 inches (0.5 millimeters) across.

    Other researchers had tested the hearing of the greater wax moth, but gave up at about 100 kHz. But the moth's ear was so sensitive at that frequency that Windmill and his colleagues wondered just how high they could hear. (By comparison, the human ear can hear sounds up to just 20 kHz)

    The research team used a laser vibrometer to measure the vibrations of the ear in response to sound waves. They also measured electrical signals in the ear nerve.

    They then watched the ear as they raised the sound frequency higher and higher.

    The researchers found that the moth's hearing went to an astonishing 300 kHtz.

    Bat versus moth
    The team hypothesizes that the moth's ultrasonic hearing could help it evade their predators in many environments.

    The moth "would probably be the food for many different bats using many different frequencies," Windmill told LiveScience.

    Bat echolocation calls can go as high as 212 kHz, so the high-frequency hearing could help the greater wax moth hear a different predator species' calls and evade them, Windmill said.

    The other possibility is that their ears help females hear the mating calls of males.

    Though male mating calls are at a lower pitch (about 80 kHz), they are incredibly short pulses. Because of how hearing works, an ear tuned to the lower pitch of the mating calls would still be moving in response to one pulse when the second was made. Being tuned to a higher frequency range could allow the females to differentiate the individual pulses, Windmill said.

    Follow Tia Ghose on Twitter @tiaghose. Follow LiveScience @livescience, Facebook and Google+. Original article on LiveScience.com.

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  • What's that smell? Moth drives a tiny robot to check it out

    Dr. Noriyasu Ando

    A close-up view of the moth steering the robot by walking on a rotating ball.

    By Tanya Lewis
    LiveScience

    Beware of robots driven by small insects. A group of researchers has put a silkmoth in the driver's seat of a small two-wheeled robot to study how the insect tracks down smells.

    Understanding the scent-tracking behavior of a silkmoth (Bombyx mori) could help scientists develop robots that are able to sense environmental spills and leaks by smell, according to the new study.

    Researchers chose to use a male silkmoth because of the distinctive mating dance it uses to zero in on a pheromone — a chemical signal from its mate. The insect moves in a straight line, followed by zigzagging, a pattern that allows it to detect clusters of odor molecules.

    Baby driver
    The moth was able to "drive" the robot by walking on a rotating polystyrene ball onboard, like a trackball controlling a computer cursor. The insect drove the robot inside a wind tunnel, which simulated the flow of air the moth would feel if it were flying. The moth drove upwind to track the pheromone. [ See Video of the Moth Driving ]

    The moth successfully located the source of the scent and drove the robot toward it in all initial trials. When the researchers covered the robot with white paper — essentially blindfolding the moth — it was still able to reach the target (the pheromone source) about 84 percent of the time.

    Then the researchers tweaked the robot to make it veer more toward one side. The moth compensated by walking in the other direction on the steering ball, making it to its target about 80 percent of the time. When the robot was made to veer to the side and also blindfolded, the moth found its target only 54 percent of the time. The results suggest the insect was steering by both its sense of smell and its sense of sight.

    The researchers also introduced a delay between when the moth sent steering commands (by walking on the ball) and when the robot actually started turning. The moth's control of the robot worsened gradually when the delay was longer, but it could still drive the robot to the goal most of the time.

    Mimicking nature
    The study builds on previous work aimed at understanding odor-guided navigation, biologist Mark Willis of Case Western Reserve University, who was not involved in the research, told LiveScience. "We don't have a man-made odor detector that's anywhere near as good as what the biological world has on offer," Willis said.

    Further experiments with the insect-controlled robot will provide a "blueprint" for biologically inspired robots, the researchers reported Tuesday in the journal Bioinspiration and Biomimetics.

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