Baron Jakob Johann von Uexkull, a Baltic German biologist, mentioned in his book entitled Stroll through the World of Animals that all creatures, including plants, on this planet live in an Umwelt (German, literally “environment”) ~ that is its own sensory world evolved to satisfy its particular requirements. A dog, a bat, a bee, a tick, a human etc. all live in the same physical world, but each perceives and interacts with it in vastly different ways. The 18th-century Italian naturalist Lazzaro Spallanzani was puzzled, for instance, by the way bats could fly in the dark, but it was not until 1938 that Donald Graffin, the American zoologist, discovered they were able to find their way by using high-frequency sounds.

The invention of the ultrasonic microphone, together with the invention of sound spectrographs has enabled researchers to listen to high-frequency sounds in the world of bats, dolphins, tree crickets and a host of small mammals. With the technical revolution during the past few decades many mysteries have been solved when scientists found that animals used environmental cues quite beyond normal human perception. On the morning of 6 May 1879, Jean-Henri Fabre, a French entomologist, found a female peacock emperor moth on his laboratory table. The moth is most commonly referred to as the Giant Peacock Moth (Satumia pyri). It is the largest moth in Europe, with a wingspan of 15-20 centimeters. Fabre kept the moth under observation by putting it in a bell-jar.

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He kept the jar in a room at night leaving one window open. What he saw that night was unforgettable. He wrote: “With a soft flick-flack the great male moths fly around the bell-jar, alight, set off again, come back, fly up to the ceiling and down … The scene suggests a wizard’s cave with its whirls of bats.” For several nights the same scenario was repeated between 8 and 10 p.m., when it was overcast and dark outside. The visitors were exclusively male moths. This fact aroused Fabre’s curiosity – what could it be that attracted the males from afar to join the female. In the inky darkness it could certainly not be a visual cue; it may be sounds having frequency below or beyond the range of human hearing, or perhaps electrical or magnetic signals.

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For the next three years Fabre tried to find out what it was that attracted only male moths. He noticed that all male moths had great plumed antennae. When he snapped them off, the male was unable to locate the caged female moth. Using other moths,........

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