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Bad Bugs, Good Designs — The Case of the Mosquito

mosquito on human skin at sunset


There are many organisms on earth that give us the creeps: spiders, snakes, ticks, and many more. Then there are countless microbes that bring disease and death. How these creatures became a part of what some call “natural evil” is an important question, but is beyond the bounds of intelligent design. ID can only look at functional information that is irreducibly complex to determine if an intelligent cause is the best explanation for its origin.

This limitation is unsurprising, since we can have the same moral agnosticism about artificial designs. A computer virus capable of destroying a nation’s infrastructure may be so well designed it eludes our national security team’s best experts. Nobody doubts the high level of intelligence behind nuclear weapons, despite their destructive power. Much as we want to leap to the “why” question, we can independently address the “what” question.

Flight: The Genius of Mosquitos

Who cannot bemoan the scourge of malaria, which kills upwards of 600,000 people per year? (CDC). Then there’s yellow fever, dengue, Zika and other diseases that plague mankind, all delivered by flying craft and injected into human skin by those familiar buzzing pests. (It must be noted that not all mosquitos in this family of 1,000 species bite humans or carry disease germs.)

A recent paper in Nature, “Smart wing rotation and trailing-edge vortices enable high frequency mosquito flight,” considers peculiarities in mosquito flight dynamics. Mosquitos (the name means “little fly”) operate unique aerodynamic equipment in unusual ways:

Mosquitoes exhibit unusual wing kinematics; their long, slender wings flap at remarkably high frequencies for their size (>800 Hz) and with lower stroke amplitudes than any other insect group. This shifts weight support away from the translation-dominated, aerodynamic mechanisms used by most insects, as well as by helicopters and aeroplanes, towards poorly understood rotational mechanisms that occur when pitching at the end of each half-stroke. [Emphasis added.]

The team of four scientists from UK and Japan must have had a challenging task. Imagine measuring wingbeats, angles, and rotations on these tiny flyers that dart to and fro constantly. Somehow, they did it, and found out that mosquitos use three methods to keep their weight aloft. (Slight as mosquitos are, they can’t fly without sufficient lift.)

We show that, although mosquitoes use familiar separated flow patterns, much of the aerodynamic force that supports their weight is generated in a manner unlike any previously described for a flying animal. There are three key features: leading-edge vortices (a well-known mechanism that appears to be almost ubiquitous in insect flight), trailing-edge vortices caused by a form of wake capture at stroke reversal, and rotational drag. The two new elements are largely independent of the wing velocity, instead relying on rapid changes in the pitch angle (wing rotation) at the end of each half-stroke, and they are therefore relatively immune to the shallow flapping amplitude. Moreover, these mechanisms are particularly well suited to high aspect ratio mosquito wings.

The second feature, unique to mosquitos among insects, is the trailing edge vortex. This is “fundamentally distinct” from the well-known leading-edge vortex, producing a flow pattern essentially reversed from the former. The trick is similar to the one used by hummingbirds, the authors note by reference. Hummingbirds’ unique shoulder bones rotate, allowing them to get lift on both wing strokes, as shown in Flight: The Genius of Birds. Here’s how it works for mosquitos:

Instead, the flow separates at the trailing edge, with streamlines reattaching further forward along the wing chord, enveloping a coherent attached vortex (Fig. 3f, t1). It is also distinct from previous descriptions of a starting vortex (sometimes referred to as a trailing-edge vortex) because it is both bound to the wing surface, rather than left in the wake, and makes a positive contribution to weight support. This transient trailing-edge vortex is quickly shed into the wake as the wing accelerates into the short translational phase, giving way to a leading-edge vortex (Fig. 3g) and a corresponding second peak in lift.

Transient is an understatement! This is happening 800 times per second, remember. The mosquito “shoulder” must be capable of flipping the orientation of the wing on each flap to gain this lift advantage. But mosquitos, of course, are not related to hummingbirds! This must be another case of that miracle of Darwinism, “convergent evolution.”

The third unique feature, rotational drag, is also interesting.

A third peak in lift occurs owing to rapid supination during the onset of stroke reversal at the end of the downstroke (Fig. 3, t3). The mechanism for this is the recently described phenomenon of rotational drag. The wing rotates initially around an axis close to the leading edge, resulting in strong forces normal to the posterior wing surface. The signature of this effect is that an intense negative pressure appears, again, in the region of the trailing edge.

These little master flyers are getting all the lift that seems theoretically possible by three independent mechanisms, two of them unique to mosquitos. Sounds like they are well designed — exquisitely so, the authors say:

The effect of leading-edge vortices is to generate sufficient lift with smaller wings; a clear advantage for flying taxa. Instead, we observed lift enhancement through two mechanisms that are exclusive to mosquitoes thus far; (i) lift enhancement due to a trailing-edge vortex captured during stroke reversal and (ii) partial weight support due to a newly described rotational effect at the end of each half-stroke. The latter mechanism, rotational drag, has been postulated previously but, here, is mediated by exquisitely timed kinematic patterns that cause a leading to trailing edge shift of the pitching axis during stroke reversal.

Good design? The proof’s in the itching; mosquitos really get around, and the female bloodsuckers always seem to find their target (us) despite our best efforts to evade them. Realize, too, that the pest you swat is equipped with compound eyes, sexual reproduction, articulated limbs, a digestive tract, respiration, a precision drill and feeding tube, saliva containing a protein anticoagulant to prevent clotting, and sensory equipment to find us by our odors and breath. Then they hone in for a precision landing in any orientation.

Who taught these miniature jet pilots about tricks that human engineers only knew about in theory? Do the scientists have any idea how these “exquisitely timed” tricks of physics evolved?

It remains an open question as to why mosquitoes have evolved to operate far outside the usual bounds of kinematic patterns used by other insects. Given that high-frequency flapping will undoubtedly incur greater inertial power requirements, one can presume compensatory selective advantages, perhaps in the domain of acoustic communication.

We get it; Come buzz for me, my love. I just evolved the coolest flight machinery. My wings flap 800 beats per second just for thee. Or, maybe that buzzing is the mosquito soundtrack from Dracula. Whatever the story they have in mind, it won’t help evolution. “Acoustic communication” implies functional information, a hallmark of intelligent design.

Faced with this clear evidence for precision flight engineering in a pest that spreads death, probing minds will ask: How did this come about? What kind of intelligence would design such a thing? Evolutionists, of course, will say that in their dog-eat-dog world of survival of the fittest, mosquitos just do whatever they can to pass on offspring, and if it means killing others, so be it. Everything is at war with everything else; natural selection favors the selfish accumulation of power. The ramifications of that belief have multiplied human death and misery on genocidal scales. Rational minds intuitively back off from that explanation.

Some might theorize that in the big ecological picture, each organism has its role that contributes to the greatest good for the most. As an alternative, they might instead posit that some original good designs became twisted for harm in the past, like robots run amok. There’s some empirical evidence supporting this view, showing that a particular agent of harm has a beneficial function in a different environment. Many of our gut microbes are beneficial, for instance.

Others insights drawing on religious teachings could be cited, including the reply to Job from the whirlwind. Such answers, though worth exploring, drift far beyond the limited scope of intelligent design. The job of ID is to identify design, not comment on its morality. We gladly leave such matters in the capable hands of philosophers and theologians. To the objective observer, mosquito aerodynamic systems look well designed. They may not get our love, but deserve our respect.

Photo credit: © mycteria —