Creation 35(2):28–31, April 2013
Browse our latest digital issue Subscribe
Butterflies fly on designer wings
Butterflies have never ceased to dazzle and amaze mankind with their colours,1 patterns, and just as importantly, their incredible flying abilities.2 The earliest recorded paintings of these beautiful creatures were found on the 3000-year-old3 tomb walls of an Egyptian named Nebamun, an “accountant of grain” (Egy. sš ḥsb it—pronounced sesh-heseb-iyt) during the reigns of Thutmose IV and Amenhotep III. The surviving fresco containing the butterflies can be seen at the British Museum in London (right). These large butterflies are thought to be Danaus chrysippus aegyptus; as common in the Nile valley today as they were back then. Did Nebamun ever wonder how such beautiful creatures could fly so effortlessly in his world of long ago? We may never know. But his tomb at least suggests he was captivated by butterflies, as I certainly am.
A casual observer might think that a butterfly simply flaps its wings up and down, but this is not so. Each beat of a rigid wing would simply cancel out the effect of the next. Butterfly wings are incredibly sophisticated. Their structure (and attachment to the thorax and flight muscles) is very complex, with both rigid and flexible wing struts (veins), tough yet flexible membranes, specially folding rear wings, and sophisticated muscle and nervous systems—and programmed behaviour to enable flight to take place.
Butterfly wings enable these fabulous creatures to find mates to renew their presence on Earth, seek out host plants upon which to lay their eggs, find sustenance, and in several well-documented cases, migrate over considerable distances, up to 4,500 km (3000 miles).4 This demands that the wings must at once be rugged enough for the demands of powered flight, yet flexible enough to enable delicate and precise manoeuvring.
Close examination has uncovered some of the secrets of how they take off. In the case of broadwing butterflies, like Danaus chrysippus aegyptus, when preparing to take off, they close their wings above their thorax and abdomen in readiness.
As the butterfly takes off, an amazing sequence takes place. The wings begin to separate, but unlike rigid membranes, they steadily peel apart as the down stroke progresses. The peel begins on the leading edges of the front wings and continues backwards until the rear wings have separated. Throughout this peeling process, a vacuum forms between the wings, drawing in a current of air from above. Leading-edge vortices5 form over the wings of butterflies during the down stroke, generating lift that draws the butterfly’s body upwards during this peel process—that lasts just 5/1000 of a second!
Throughout this initial down stroke, the body is not only propelled upwards but also tilted backwards from the horizontal. This backward pitch is no mistake. It positions the butterfly body correctly for the return upstroke, during which the wings now travel horizontally in relation to the ground. At the same time, the leading edges of the forewings curl upwards. This enables the wings to keep a positive angle of attack, producing vertical lift to continue the upward momentum of the down stroke.
A puzzle solved
An apparent conundrum is that during the peel, air should, logically, be drawn in from behind also. This would cancel the effect of air coming from the front, compromising lift-generation. Fortunately for the butterfly, it has a brilliant design feature that prevents this. Its flexible anal lobes (that part of the rear wing closest to the abdomen) act as an efficient valve that prevents any retrograde airflow; at least until the peel process is complete. In this ingenious design feature, the rear wing is able to fold along a groove called the claval furrow. This allows the butterfly to keep a secure seal during the upstroke, whereas an inflexible rear wing would not make an airtight seal possible, being obstructed by the insect’s body.
This butterfly mechanism is usually referred to as ‘clap and peel’.6 However, not all butterflies use this exact sequence of movements (see below).
A scientific study made the following observations: 7
“In successive wing-beats, Vanessa atalanta can choose to use, or not to use, wake capture, leading-edge vortices, a clap and peel mechanism, and whether to use positive, negative or zero loading on the upstroke.”
“The butterflies in our experiments used all of the unsteady aerodynamic mechanisms that have been proposed. They switch between mechanisms freely—often using completely different mechanisms on successive wing strokes—and are able to choose different aerodynamic mechanisms to suit different flight behaviours.”
Interestingly the butterfly brain which makes all these flight decisions (and multitudes of other daily directives) is not much larger than the dot atop this ‘i’.
Despite the clear implication of design in the sophisticated flight mechanism of butterflies, evolutionary thinking requires considerable denial, as Romans 1:20 reminds us. A typical comment: “State-of the-art fighter planes are ‘fly-by-wire’: they depend on continuous adjustment of the wing surfaces by advanced computer control … Insects, however, manage the complex manoeuvres of flight instinctively, using ‘fly-by-wire’ aviation skills that evolved over 100 million years ago.”8
But modern aircraft are created by intelligent designers, built by intelligent constructors, and sustained by intelligent programs written by intelligent beings that control the machines. Amazingly, evolutionists believe that insects, including butterflies, garnered all the elements required for flight (muscles, wings, scales, sight, lift, etc.) by random mutations filtered by the demands of the environment.
A leading butterfly researcher admits: “The study of evolution inevitably involves much speculation and inference, and it would be a mistake to imagine that we understand the course of evolution in butterflies.”
He goes on to say (emphasis mine): “All we can say is that various studies made so far are largely consistent with the idea that evolution progresses through a continual interaction of accident and selection … butterflies are just good enough to get by.”9
Really? Modern man prides himself on his ability to design fixed wing aircraft that generate lift at great effort and expense. Yet the Creator has designed something far more sophisticated that enables all butterflies to use flexible wings to efficiently generate lift on both upstroke and downstroke, without polluting the environment. And, as an added bonus, they can replicate themselves, unlike man-made aircraft. Yet consistent with their naturalistic belief system, evolutionists are forced to claim that butterflies are “just good enough to get by”.
These surprisingly hardy creatures have survived the Fall, the Flood, and myriad man-made changes to their environments, yet still they continue to prosper, and to amaze mankind. Do you still think that butterflies merely ‘flap their wings’, or can you now see more clearly the creative hand of God?
Amazing variety of design
One particular variant of butterfly stroke commonly called ‘funnel formation’ takes creative design to new heights. Here our focus is on what happens immediately after the wings pause at the end of the down stroke.
The wing tips just touch at the beginning of the upstroke: at this point this is a mirror image of the opening phase of the down stroke. As the upstroke progresses, however, two distinct flexural forces begin to simultaneously act on the wings—one along the chord10 of the wings from leading to trailing edge; the second acting at 90˚ to the first.
The two forces draw the wings into a funnel; the leading edges form the mouth, and the trailing edges compose the tapered body. As the funnel enlarges, air flows into the funnel mouth and the rear wing seal maintains the flow.
The funnel effect works until the wings separate: the instant that air leaks past the wing tips the effect is gone. The bonus for the butterfly is that by this point in the wing cycle the funnel has done its job; the wings are now moving fast enough for conventional aerodynamics to take over and generate sufficient lift.
References and notes
- The bright iridescent blues in some butterflies are due to the elaborate diffraction gratings formed by their wing scales. See Sarfati, J., Beautiful black and blue butterflies, Journal of Creation 19(1):9–10, 2005; creation.com/blue. Return to text.
- Wieland, C., Butterfly blast (interview with Bernard d’Abrera, author of the authoritative volume The Concise Atlas of Butterflies of the World), Creation 25(3):16–19, 2003; creation.com/butterfly-blast. Return to text.
- This is not the secular Egyptological 14th century BC date found in the secular literature, but is in accord with my work on a revised Egyptian chronology that agrees with the Bible timeline. Return to text.
- Poirier, J., The magnificent migrating monarch: An electronic design expert ponders the stunning navigational exploits of the monarch butterfly, Creation 20(1):28–31, 1997; creation.com/monarch. Return to text.
- Plural of vortex = a mass of fluid (like air or water) spinning around a centre. Return to text.
- Catchpoole, D., Why a butterfly flutters by, Creation 26(2):56, 2004; creation.com/butterfly. Return to text.
- Srygley, R,B., & Thomas, A.L.R., Unconventional lift generating mechanisms in free-flying butterflies, Nature 420:660–664, 2002. Return to text.
- Vane-Wright, D., Butterflies, p. 50, The Natural History Museum, London, 2003. Return to text.
- Ref. 8, p. 95. Return to text.
- The imaginary straight line joining the trailing edge and the centre of curvature of the leading edge of the cross-section of an airfoil. Return to text.
Comments are automatically closed 14 days after publication.