Hearing with ears
 Most
animals have ears near their brain. Do any animals hear
with ears on their legs?
April Holladay
Published on Monday, April 12,
2010 12:01 PM MST
Crickets have
ears on their front legs, located about where humans have elbows. Katydids
also have leg ears.
In fact, ears "(tympanal organs) lie beneath a drum-like membrane (the
tympanum) where they respond to sound," says entomologist
John Meyer,
professor at North Carolina State University. These 'ears' may be
located on the thorax (in some true bugs), on the abdomen (in grasshoppers,
cicadas, and some moths), or on the front tibia (in crickets and katydids)."
Name a creature which uses its legs to hear. Alexud, Pensacola, Florida,
USA
A calling male cricket creates a racket — chirping loudly at a fixed
frequency that depends on his species and the night temperature. A
female hears the beckoning calls, determines the direction of the chirp source
and tracks down the male chirper, "purely based on
auditory cues," says zoologist
Martin Lankheet
of Wageningen University. She distinguishes
direction by listening to the time difference she hears from her right
and left ears.
The two ears consist of eardrums (small, pale spots) spaced about 12
millimeters (0.5 in) apart on her left and right legs. She hears a sound
coming from right of her position, for example, with her right ear before she
hears it with the left. The time delay tells the direction of the chirping male.
Perhaps crickets developed ears on their legs to increase the separation
distance between their ears. Indeed:
"Because crickets are very small compared to the wavelength of male sounds,
an increase in the separation distance increases the difference in signals
between the two ears. Moving the ears further apart therefore helps direction
discrimination, and mate finding," emails Lankheet.
More exploring
Frogs'
Hearing, WonderQuest
A
closer look at cricket hearing, email from Martin Lankheet.
Further Reading:
Cricket directional hearing by Martin Lankheet, Wageningen University, The
Netherlands
Mechanorecptors by John R. Meyer, North Carolina State University
April Holladay lives in Albuquerque,
New Mexico. Her column, WonderQuest, appears every second Monday of the month
on WonderQuest.com. To read April's past columns, please visit her
website . If you have a question for
April, visit this
information page
(Answered April 12, 2010)
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