January 14, 2021 | David F. Coppedge

Fly Specialties Amaze Scientists

The humble housefly deserves some respect for its engineering design.

Houseflies have specialised wings that make them harder to swat (New Scientist). We’ve all experienced the frustration of sneaking up on a fly, only to have it zip away as the swatter is coming down. They seem to have a control tower informing them of an incoming hazard. How do they get away so often? This Darwin-free article says that their engines rev up for take-off periodically as they stand on a surface.  A team at Case Western Reserve University led by Alexandra Yarger found that these insects use more than their eyes to achieve rapid take-off.

All fly species have shortened hindwings called halteres. These don’t generate useful lift, but are used as sensory organs for balance to help stabilise the insect while in flight.

A group of flies known as Calyptratae, which includes houseflies and blowflies, rhythmically move these wings when standing.

Halteres have been known for a long time to stabilize flight. An early Moody Institute of Science film showed the flies wobbling uncontrollably without them. The rhythmic motions of the halteres when standing, though, adds a new function. High-speed cameras showed that this revving up increased the fly’s take-off speed by five times. The trick is achieved without added delays of the nervous system, they believe.

“We think there might be a pathway from halteres to the legs that’s causing them to take off faster,” says Yarger. “It doesn’t go through any central nervous system, it’s almost like a reflex,” she [Yarger] says.

A Cop-Out: Darwinizing Design

A fly’s eye view of evolution (University of Göttingen). A photo in this press release shows the astonishing pattern of hexagonal facets in a fly’s eye. A good view of the geometric precision of these facets (called ommatidia) in an insect eye can be seen close up at 01:30-01:45 in Cristobal Vila’s beautiful animation, Infinite Patterns. As shown in the diagram at right, each facet is like a complete eye of its own, with a lens, pigments, waveguides and photoreceptors, each one connected to the whole with neurons. This segmented eye plan allows an eye to curve around a hemisphere to give the insect a nearly 360-degree field of view.

The segmented design also allows for a multitude of variations depending on the lifestyle of each insect; genera or families can be fit to the needs of the insect by regulating the number of facets formed rather than multiplying genes – something like looping a subroutine with a counter in a computer program instead of repeating the whole code multiple times. It’s an elegant solution to generating a theme and variations. A beetle that lives in the dark can get by with fewer facets; a dragonfly that relies on sunlight to capture prey with rapid flight maneuvers can have many thousands of facets more. The observed differences in facet count is noted in the press release:

Anyone who has seen hoverflies manoeuvring through the air and, quick as a flash, changing direction, has probably witnessed a mating attempt in which the male, with breath-taking accuracy, pursues a fast-moving female. To carry out this specialised visual task, the huge compound eyes of hoverflies consist of up to 6,000 individual facets. There are special individual facets directed towards the sky that show particularly high resolution. In contrast, bark beetles, which spend most of their time burrowing inside wood, rarely rely on visual information. Hence, they have developed very small eyes with a maximum of 300 facets.

Is evolution really needed to explain this? Readers are subjected to the hypnotic stare of Dr Nico Posnien, who ascribes the design to Darwinian magic. Things “emerge.” Things “arise.” Things “evolve.” The unsuspecting reader is swept up by the repetition of miracle words to believe that, when it comes to complex visual systems, “Stuff Happens.”

  • In the course of evolution
  • …an enormous variety of eye sizes and shapes has emerged
  • The study was published in the journal Molecular Biology and Evolution.
  • … they have developed very small eyes…
  • …a diversity of size and shape of eyes can arise
  • …arose several times independently in evolution
  • …contributes to a better understanding of the evolution of complex organs…

This article strains at a gnat and swallows a camel, thinking only about the number of facets, without pondering the improbability of chance mutations accounting for a functioning eye. Surely the greater challenge to a Darwinist is accounting for the whole visual system itself, not just the number of facets. Each facet must be tuned to the type of light encountered in the insect’s habitat. These facets moreover, must also be integrated into the brain and the entire animal. That’s where the biological challenge is: how did such integrated operational machines become incorporated into an insect as small as a fly?

Despite the repetition of evolution-words, the original paper begins, “Revealing the mechanisms underlying the breath-taking morphological diversity observed in nature is a major challenge in Biology.

We propose that natural variation in expression or function of highly connected developmental regulators with pleiotropic functions is a major driver for morphological evolution and we discuss implications on gene regulatory network evolution. In comparison to previous findings, our data strongly suggests that evolutionary hotspots are not the only contributors to the repeated evolution of eye size and head shape in Drosophila.

Their thesis is not classic Darwinism after all. If natural variation in gene expression is taking place in existing gene networks, and if the mutations are not random but are occurring in “hotspot genes,” scientists should investigate whether there is a built-in engineered process going on. A process for robustness against perturbations that allows flies to quickly adapt to changing environments would be a design feature, not evolution.

Darwinian evolutionary theory adds nothing to the science here. If facet numbers are controlled by pre-existing gene regulatory networks, then variations might be attributed to adjustments at those nodes. A design approach might see variability in facet numbers attributable to tuning of genetic switches or rheostats. Changes there could adjust the gene regulatory network to inputs from the environment.

Saying “it evolved” is a cheap way out of the work of a scientist to explain complex phenomena. An evolutionist might counter, “Well, so is explaining something by saying ‘God did it’.” The difference is that chance is not an explanation at all (i.e., “it evolved” is equivalent to “stuff happens”). In our uniform experience, though, we know that any time a complex, functioning machine is observed coming into existence, its cause can always be attributed to intelligent design. An inference to design, furthermore, opens up many new questions to address, and makes predictions that can be followed up using the scientific method. Think of the science-promoting potential of asking, “If something works, it’s not happening by accident; so what is it doing?” Saying “it evolved” is a science stopper.


Exercise: Role play a Christian parent whose fifth grader is asking about an article she just read, “Curious Kids: How did some animals evolve wings to fly?” (The Conversation). Give age-appropriate answers, perhaps by asking questions like, “How do they know that?” and by teaching some lessons from the Baloney Detector. If you don’t know scientific facts to refute the claims, you can say, “I don’t know; let’s find out” and make it a joint project to look up some answers from creation sites. One answer you should not use is, “Oh, we don’t believe that evolution stuff.”


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