Summer School Lessons from Actias Luna

Rediscovering a Natural Flying System through the Eyes of Design

For the nature-lover, the season of summer brings many welcome insect visitors - perhaps making one man’s dread another’s delight. At the time of this writing, many in the Northeastern and Midwest portions of the country are enjoying the Brood X cicadas, which emerge in earnest every seventeen years. Regaled by the percussive noise of the cicadas by day, by night Midwesterners are also treated to the chirping sounds of katydids and spectacular light shows by our several species of fireflies. For insect lovers, the summer season becomes a festival of marvelous sights and sounds (mosquitos notwithstanding).

My affinity for summer six-legged visitors was fully manifest recently in a local grocery store parking lot by night, while loading groceries into my car. Captivated by what at first appeared to be a small model glider, I abandoned car and cart to chase this wonder across the parking lot. Having lost sight of it, I breathed a prayer “God, please send that thing back to me, please send it back,” and to my fortuitous wonder, it flew right past me – so close my husband said “duck!” after which it lighted on a tree in nearly perfect camouflage. With phone cameras quickly drawn from pocket holsters we captured the Luna Moth (Actias luna) in still images and video, which were promptly shared on family text threads and social media.

For days after I continuously wondered at this lovely creature. A. luna sports a rather large wingspan for a moth at approximately four inches or more – which is why at first it appeared to be someone’s rogue model glider - and an unusual tail that flaps while in flight. As a recovering well-entrenched Darwin apologist, I felt obliged to ponder how evolution – or purely unguided, mechanistic forces - could have fashioned such a biological flying system so perfectly. A few key things, however, belied this notion: most significantly my past experience as a model airplane builder and flyer, along with a personal discussion with a retired Lockheed-Martin aeronautical engineer.

Design in Simple Man-Made Flying Systems

When model builders build airplanes to fly (as opposed to merely display), it is crucial that they follow with demanding precision, the directions on the airplane plan. These plans are not designed willy-nilly, but rather by very experienced hobbyists and engineers, who go through a painstaking process to prototype the design, build the craft, trim, and fly it. As any model builder can tell you, there are more ways to crash an airplane than there are to successfully fly it – entropy is huge, as many flight parameters can speedily send a nascent plane to certain doom.

A quick glance at any model airplane plans reveals that there are many constraints for building that must be observed: such as using the right density balsa, tissue and other materials; gluing struts, ribs, and stringers together with exacting precision; and using exactly the outlined materials for propellors and landing gears, to name but a few. Even when these parameters are diligently met, oftentimes the most adroit and experienced fingers do not produce an aircraft that flies perfectly in its first maiden flight. It will require further “trimming.”

In the business of getting the airplane to actually fly, many issues arise, requiring adjustments by the modeler: such as the placement of the center of gravity (“CG”) with relation to the wings (as a misplaced CG can cause the craft to nosedive)¹. This is often ameliorated by placing a clay mass on the nose or moving the position of the actual wing. Another consideration is the angle of attack (that angle at which the wing hits the air to generate lift), along with using rubber band motors of just the right width, length, and number of winds. If the rubber band motor does not meet specifications, the airplane will have too much power and crash, or not enough power to generate lift, or even enjoy an enduring flight. These are but a fraction of the factors modelers have to take into account when flying these “simple” airplanes. Competition-level model aircraft then, are not only the consequences of the foresight of a design engineer, but also the beneficiaries of the builder’s fine tuning and trimming after they are built.

Design in a Biological Flying System

Likely it was this experience as an airplane modeler that enabled me to all the more appreciate the elegant and adroit flight of my newfound six-legged friend. This particular biological flying system - in a similar fashion to flying model airplanes - exemplifies what biochemist and author Michael Behe calls a “purposeful arrangement of parts” belying the ability of the random, undirected, and blind forces of evolution to yield. Behe remarks, “whenever we see independent pieces ordered to each other to make a coherent whole, we always strongly suspect design,” adding, “[t]he more pieces there are and the more closely they are matched to the whole, the stronger and  stronger is our confidence in the conclusion of intelligent design.”²

My continued appreciation of the moth prompted a conversation with Thomas Stroup, a retired career engineer with Lockheed Martin. He confirmed what many of us already knew – to build large-scale flying systems, there are countless sensitive design inputs that must be considered. In changing any one of these single variables (inputs), several others likely require adjustments, accordingly, confirming Behe’s observations that whenever we observe independent pieces ordered to make a coherent whole, we are prone to suspect a designer’s hand (in this case, a team of Lockheed engineers).

In discussing A. luna in particular with Mr. Stroup, he remarked that the biological materials the moth uses are extraordinary. He pointed out that the wings are durable enough to sustain crashes with relatively few tears; the wing material enables tight folding and unfurling as it emerges from its cocoon; and is flexible enough to enable a circulatory network of lymph through its many vessels. He was quite impressed as well that the moth is in effect “trimmed” and ready for flight after it leaves its cocoon. Remarkably still, the flapping tail of the moth mentioned earlier functions as a distraction to ward off predators.

When I asked Mr. Stroup if he thought it was possible for blind and unguided material forces to generate a flying system as complex as the Luna Moths, he paused, reflected, and added that the animal carries out very complex tasks than could rival any human-designed aircraft. “Human engineers build aircraft to safely and efficiently transport people and cargo; Luna Moths are tasked with flight, reproduction, escape from predation, camouflage, and survival making an evolutionary mechanism not plausible.”

Surpassing Human Engineers

Indeed A. luna is quite a marvel sporting sophistication surpassing even our highest tech man-made aircraft. As Mr. Stroup and I discussed the moth, we both could not help but express wonder, sheer wonder, at its construction, maneuverability, and design. Mr. Stroup is like many engineers, in that he recognizes the signposts of design.

Finally, this organic flight system – unlike man-made ones – carries out its varied functions for survival with perfection; without enjoying the affordances that come with iteration. While man-made engineered systems demonstrate tremendous foresight in their designs, they still undergo an iterative process of prototyping, trials, performance evaluation, and redesign. Even the most skilled team of engineers are still limited in ascertaining every contingency their designs will encounter once in full use - as they may be brilliant - but they are not all-knowing. That engineer having existed in eternity-past responsible for the elegant design of A. luna was, however, privy to every circumstance for its survival, having been responsible for creating those circumstances as well; consequently, iterations were not necessary.

So this summer, if you have the opportunity to spot one of these elegant creatures, take a moment to ponder and reflect how it truly is an engineering marvel, coming from the drawing board of an extraordinary engineer.

NOTES:

1. Simons, M. (1999). Model aircraft aerodynamics, 4^th edition. Special Interest Model Books, Ltd.
2. Behe, M. J. (2019). Darwin devolves: The new science about DNA that challenges evolution. HarperCollins.