The Evolution of Aerial Combat

Luna moth resting on a screen at the Len Foote Hike Inn in north GeorgiaIMG_3015

This was one of a few luna moths we saw while we were hiking this May in Amicalola Falls State Park in the north Georgia mountains. With apparently little to do in the daylight hours, these huge specimens mostly just hung around our lovely accommodations at the Len Foote Hike Inn. When nighttime comes, things might get a bit busier.

Luna moths, as large and impressive looking as they are, have little chance against the weight and teeth of a hungry bat. But as long ago as 1903 a published report suggested that the extended hindwing tails dragging behind the wings of saturniid moths, the family of moths that include luna moths, might serve to divert bat attacks away from crucial parts of the moth’s body. The hindwing tail may present an acoustic return of the bat’s sonar that proves more attractive than the main wings and body of these moths. Evidence of this was discovered by Jesse Barber and colleagues at Boise State University and the Florida Museum of Natural History.

The expendable hindwing tail does little to improve basic flight.IMG_3014

They presented luna moths with and without their hindwing tails to big brown bats in controlled settings and found that bats captured only 34% of moths with intact tails, but captured 81% of bats with their hindwing tails removed. Tail removal did not otherwise injure or significantly alter the flight characteristics of the moths.

The link below is infrared video of a big brown bat’s unsuccessful attack of a luna moth. The bat appears to aim for the hindwing tail, and even though the moth seems to lose part of its tail in the attack, it escapes.

BAT ATTACK VIDEO

Between 1937 and 1942, human technology, perhaps unknowingly, perhaps not, suggested imitating nature. British researchers thought that dropping strips of aluminum foil from aircraft might deflect German radar and allow British bombers to remain undetected as they approached targets over Germany during World War II. They called this dropped chaff, Window, and it appeared to work. German fighters could not be vectored to meet the approaching bombers, and ground-based anti-aircraft fire had to rely on visual sightings rather than advance alerts from radar.

Today, military aircraft flying in harm’s way fire flares behind them to distract enemy anti-aircraft missiles. The heat of the burning flare will attract the heat-seeking missile away from the vulnerable and slow-moving aircraft.

Seahawk helicopter firing anti-missile flares.chaff_Seahawk

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Jesse R. Barber, et al. 2015. Moth tails divert bat attack: Evolution of acoustic deflection. Proceedings of the National Academy of Sciences, Vol. 112 no. 9, p. 2812–2816, doi: 10.1073/pnas.1421926112

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