Leg Senses Sound Strength and Direction

close up photograph of yellow grasshopper on log

Biological Strategy

Grasshoppers

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Sense Sound and Other Vibrations From the Environment

For living systems, sensing sound and other vibrations is important for communicating and detecting conditions within their environment. Living systems must locate a signal’s source so that they can move toward it (such as when it is food or a potential mate) or away from it (such as when it is a predator). To prompt an appropriate response, living systems must sense these signals, recognize their amplitude or volume (which is sometimes very low), and determine their direction. Living systems must be attuned to signals relevant to them and able to distinguish these from irrelevant sounds to avoid expending unnecessary energy. For example, owls’ ears are asymmetrically placed. This enables them to detect sounds more accurately, which helps them locate small prey at night and avoid wasting energy chasing down irrelevant sounds.

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Insects

Class Insecta (“an insect”): Flies, ants, beetles, cockroaches, fleas, dragonflies

Insects are the most abundant arthropods—they make up 90% of the animals in the phylum. They’re found everywhere on earth except the deep ocean, and scientists estimate there are millions of insects not yet described. Most live on land, but many live in freshwater or saltwater marshes for part of their life cycles. Insects have three distinct body sections: a head, which has specialized mouthparts, a thorax, which has jointed legs, and an abdomen. They have well-developed nervous and sensory systems, and are the only invertebrate that can fly, thanks to their lightweight exoskeletons and small size.

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Grasshoppers detect sound and the direction of its source with leg membranes.

“Grasshoppers listen with their legs. They have two slits on the first pair of thighs which lead to deep pockets. The common wall between these forms a membrane which is the equivalent of an eardrum. The angle at which sound strikes the slits affects the strength in which it reaches the drum, so the grasshopper, by waving its legs in the air, can discover the direction from which a call is coming.” (Attenborough 1979:94)

Last Updated August 18, 2016

References

Book

Life on Earth: A Natural History

Little, Brown and Company | 01/01/1970 | David Attenborough

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