Insects may seem very small on the evolutionary scale of earth’s biosphere. However, these tiny animals contain very sophisticated tools used to communicate with each other through sound. Some vibrational patterns exist above or below the auditory sense abilities of humans, yet several studies back claims that insects process sounds much like concert musicians notice very slight changes in pitch, according to National Public Radio. Two entomologists have dedicated their lives to the study of insect sounds, and both of them realize how complex the ears of insects can get.
Rex Cocroft of the University of Missouri studies how treehoppers transmit sound waves through tree branches to communicate with other. Males use muscles in the thorax and abdomen to undulate the abdomen. These undulations travel through the fleshy stems of plants. Nearby males and females can sense these vibrations up to 3 feet away.
Cocroft demonstrated the concept with a phonograph needle cartridge connected to an amplifier. Soft purring sounds emanated from the device, but human ears cannot pick up the low sound without the amplification. Treehoppers communicate with each other to warn of predators and to find mates. Even more amazing, other creatures with larger ears cannot even hear these secret signals.
Laurel Symes of Dartmouth College takes a different approach to insect vibrations. She studies how crickets can discern distinct chirps among various species. Unlike treehoppers, humans can detect crickets when they send out their calls. However, a forest full of crickets all sound the same.
In order to detect one type of cricket from another, females can discern very small changes in the calls of males. Symes experimented with different cricket calls with startling results. The scientist amplified the sounds produced by the males of one species of cricket in front of two groups of female crickets from different species. One species’ females became very interested in the sounds while the others didn’t. When Symes changed things up and switched to amplified sounds of the other species, the opposite group of females reacted.
The sounds coming through Symes’ amplifiers sound the exact same to humans. However, one species emits sounds at 43 pulses per second while the other sounds off at 51 pulses per second. Human ears can’t tell the difference, but the two species of crickets can. North America alone harbors 140 different species of crickets, so the importance of this discernment becomes clear. If a female can’t detect a male of her species, she can’t mate. On a large scale, this means crickets would become extinct without special hearing abilities.
Insects need to have extremely discriminating sound detection organs because a small section of forest teems with minuscule life forms that produce a cacophony of sound. Without very sensitive auditory organs, insects can’t warn each other of danger, nor can these creatures find mates.
Insects hear things through sensitive organs on their legs called tymbals, notes Home Science Tools. Some insects, such as crickets, grasshoppers and cicadas, rub their legs against other parts of their bodies to produce sounds. Tymbals then receive sounds as vibrations travel through the hollow membranes within the insects’ legs. Other insects, such as bees, create sound by flapping wings. Hissing cockroaches native to Madagascar breathe through hollow tubes to make vibrations.
These small creatures produce sound very efficiently, states Map of Life. Minuscule body parts can vibrate very rapidly due to their small size. Airborne sounds have much higher pitches than those that travel through plants. The need to communicate beyond the hearing of other animals led to insects capable of detecting each other’s sounds despite bird calls, raindrops, wind and other airborne noises from animals. Hundreds of millions of years of evolution have produced insects with extremely sensitive hearing, so much so that 90 percent of the world’s bugs rely on this type of communication to survive.
Amplify hundreds of animal noises through a very loud rainforest, and the importance of insect hearing becomes clear. If humans could learn to study these hearing mechanisms through technological means, imagine the concepts scientists could explore as humans develop ways to combat hearing loss, improve sound transmission, and cure deafness. Learn more about these amazing, tiny animals through The Rainforest Site.Whizzco