Tiger Moths And Bats

Bats are active at nights. Most of them hunt for insects by sending high pitched sounds (Sound is made by vibrating things. The faster things vibrate, the higher the pitch. The rate at which vibrations are produced is, pitch).

Bats produce sounds by their mouth or nose. When the sound waves hit an object an echo comes back. The bat’s ears have a complex set of folds that help determine the position of the object. Based on the intensity of echo, a bat can know how big an object is. A smaller object will reflect less sound waves and the echo will be small. If the object is an insect, the bat can know in which direction the insect is moving. A lower pitch echo will mean that the insect is moving away and a higher pitch will mean the opposite. This mechanism is known as echolocation. Bats navigate themselves and hunt insects by echo locating objects and prey. A wide variety of insects are eaten by bats, except Tiger moths.

Tiger moths belong to the family Arctidae. They are world wide in distributio0n. Most of them are night fliers. They derive their name from their bold contrasting coloration of gold and black, resembling the stripes of a tiger. The wings are thin and elegant, having fine scales and a span of ¾ to 3 inches. The larvae of Tiger moths, the woolly bears feed on a variety of plants and accumulate toxins in their skin. Adult moths acquire these toxins. They are therefore bad tasting insects.

The Tiger moth has survived bat predation over millions of years. The moth has a special organ called Tymbal organ on its meta thorax. This organ has thin membranes which are vibrated to produce ultrasonic sounds (high pitch sounds similar to bats that humans cannot hear).The moth has also a Tympanal organ on the thorax which functions as a hearing organ.

With this apparatus, the Tiger moth is capable of hearing bat’s sounds. It evades the bat, by a series of evasive maneuvers of loops, spirals and dives. It produces high frequency click sounds or squeaks. These sound waves perceived by the bat as multiple echoes, leave the bat confused and unable to locate or target the moth.

It was earlier believed that the Tiger moth jams the sonar system of bats by its ultrasounds. But experiments have revealed that the Tiger moth is more intent on making its presence felt by its sounds and warn the predator of its toxins and bad taste. It is more a chemical message to bats to seek their dinner somewhere else.

The aerial battles of Tiger moths and bats continue to baffle scientists.