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Wednesday, December 8, 2010

Katydids sing for lunch!

Cicadas are small insects found in many parts of the world but largely in Australia. There are about 2500 species of cicadas. There are many facts that can be discused about this tiny creature but this essay pinpoints on the cicadas mating strategy and an interesting twist discovered by cicada experts Dave Marshal and Kathy Hill of the University of Connecticut.

Male cicadas have very loud "noise makers" called tymbals on the sides of their abdominal base. Unlike in grasshoppers in which the sound is created through stridulation (rubbing of one body part against another), the sound created by male cicadas is due to the contraction and relaxing of the muscle obn their abdominal base. The sound created can be as simple as a "click" or very complicated and including a chorus. So only male cicadas have "sound makers" but both the sexes have "sound detectors" called tympana which are literally the cicada's ears. An interesting note is that male cicadas have the capability to "disable" their earing instruments when they are creating a sound. This is a very useful strategy because cicada sounds are the loudest among all insects. If the cicada were laid on a human's shoulder - close to the ear - and created a sound, the human would be permanatly deaf. Some of the notes created by cicadas are so high pitched that the human ear can't even detect. (pictured above is a group of cicadas)

When a male cicada is looking for "love", he starts creating a sound. It is timely to mention that each specie of cicada has a unique type of sound; this aids the female cicada in detecting whether the male cicada calling out is her type or not. Cicadas love heat and "sing" their most spirited "songs" in the hotter days of the year.

If the female cicada responds to the song of the male cicada, that's a sign that he has been chosen. The singing and responding will continue untill the male finds the female cicada.

Researcher such as Hill and Marshall have found that snapping your fingers can attract the attention of the male cicada. But it is all in the timing. The female cicada responds to the male's signal in about 70 miliseconds which means seven hundredth of a second. If the timing is right, the male cicada will be fooled.

So, what's the twist?

On a journey which led Marshal, Hill and Max Moulds to Queensland, Australia, the researchers came upon a very interesting note. After hearing the reply of ehat seemed to be a female cicada, one of the researchers tracked down the source of the sound and was amazed at what he observed. The source of the reply wasn't a female cicada but a well camouflagued Katydid.

Katydids or Bush-crickets are an excelent example of mimicry and camouflague. As seen in the example above, the katydid mimics the sound of a female cicada in order to attract the male cicada towards itself and gobble it up. (pictured above is a katydid)

The researcher also foreshadowed that "Captive Katydids respond to almost any sharpand short sound, like the clik of two coins or even the sound of a car's indicator."


Reference: New Scientist magazin, 26 September 2009, page 44-7  visit: http://www.newscientist.com/

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