Remember the days when you assembled model aircraft after Christmas or a birthday, and hung them proudly from the bedroom ceiling? If you were especially skilled, you assembled ones that could actually fly. You would be the first to boast that success didn’t happen by chance. But now, imagine assembling a working model a hundred times smaller.
Avian flight is a work of genius, as Illustra’s documentary Flight amply illustrated. But in a way, miniaturization is even more a mark of genius. Packing the power of a 1960s mainframe computer into a wristwatch took decades of work by thousands of scientists and engineers at Apple and other companies. When you compare a pigeon to a gnat, and realize they are both excellent flyers, you really have to think about where all that miniaturized design comes from. Let’s look at some recent findings in insect aviation.
Speaking of miniaturization, remember the geolocators attached to arctic terns in the Illustra video? Now they’re putting devices on beetles! Watch the video clip above from UC Berkeley. The one-gram electronic backpacks attached to giant flower beetles allow researchers to learn how the muscles work, and how the wings control steering. For technical details, see the article in Current Biology.
Entomologists (insect experts) used to think that the hard outer shells that give beetles their order name "coleoptera" (sheathed wing) were just that — protective shells over the flight wings. It turns out these outer shells help with steering.
"Since the 1800s, this coleopteran muscle was thought to function solely in wing folding," said study lead author Hirotaka Sato, an assistant professor at NTU’s School of Mechanical and Aerospace Engineering. "Our wireless system allows us to record neuromuscular movements in natural, free flight, so we see now that this muscle is also used for turning." [Emphasis added.]
The radio-controlled backpacks were equipped to stimulate some of the muscles. This allowed the team to manipulate the insects, making them turn right or left, and watch their reactions with high-speed cameras. Next, the engineers think they could add a microphone and thermal sensor. Who knows; someday this knowledge may allow search-and-rescue workers to gather data from hard-to-reach locations.
Now if they can get a backpack to fit on a gnat, they’ll really be showing off some intelligent design! Even so, it will only force us to consider that a gnat has much more equipment: wings, muscles, nerves, digestive system, and flight software all packed into that tiny speck of a living organism — plus the ability to reproduce all those parts!
Moving down the size scale from the beetle, let’s look at bees, and consider a question only a scientist might think of: "Do honeybees learn to follow highways?" Actually, they do, say Thomas Collett and Paul Graham in Current Biology. "Radar studies of a honeybee’s flights when it first leaves its nest suggest the features of the surrounding landscape that it learns guide future foraging trips." If you were a bee on your first flight, what would you look for?
Orientation or learning flights are performed on the first few departures of a wasp or bee from its nest, when it learns the position of the nest relative to its near and far surroundings. The flights are intriguing because they contain elaborate manoeuvres that are likely to be adapted to acquiring navigational information. They begin with a portion within about 0.5 m of the nest often lasting about 20-30 seconds, which can be recorded with video. These manoeuvres and their possible function in gathering information are to some degree understood. The likely role of larger-scale flight patterns is more uncertain.
Three recent studies, the authors say, show that bees learn to follow straight lines, like hedgerows and highways, as guideposts for future flights. Once again, the scientists learned this by attaching tiny radar transponders to the insects. Electronic devices are making this a golden age for studying flying insects of all kinds. Here’s an example of "convergence" that design advocates will like:
Use of this methodology is likely to uncover much detail about the array of strategies that enable honeybees to navigate within a familiar landscape. The data so far suggest a convergence between birds and bees. A decade ago it was found that homing pigeons follow conveniently placed man-made roads on their way back to their lofts. It now appears that honeybees may also exploit linear features of a landscape as offering economical and reliable navigational guides.
Be sure to tell your children this part of the story of the birds and the bees!
Probably the best flyers in the insect world are dragonflies. They can hover, move forward and backward, mate on the wing, and capture prey in half a second from launch to interception, succeeding 95 percent of the time. How they hunt so successfully was recently described in Nature by a team led by Anthony Leonardo of Howard Hughes Medical Institute. In the same issue of Nature, Harvard biologist Stacey A. Combes summarizes the findings in a news article titled, "Neuroscience: Dragonflies predict and plan their hunts." Combes begins with this picturesque metaphor:
Imagine a ballet dancer moving across the stage to meet his partner, who is leaping and pirouetting towards him. To catch her at the right moment, he must predict where she will end up and determine how he should move to intercept her. To do this, his mind anticipates how her image should grow as they move towards each other, allowing him to rapidly identify and react to unexpected changes, such as a stumble that lowers her speed. Until now, this type of complex control, which incorporates both prediction and reaction, had been demonstrated only in vertebrates. However, in this issue, Mischiati et al. (page 333) show that dragonflies on the hunt perform internal calculations every bit as complex as those of a ballet dancer.
News from HHMI shares highlights about the "complex choreography" of the dragonfly hunt. Researchers used to think that the insects just kept on eye on the prey and moved accordingly. It’s "more complicated" than that, the new research shows; dragonfly also knows the positions and reactions of its own body as it flips and turns:
Those shifts in orientation create a challenge for the predator. "The dragonfly is making a lot of turns to line itself up. Those turns create a lot of apparent prey motion. If the whole world is going to spin, how can it possibly see its prey?" Leonardo asks. Surprisingly, the scientists found that each dragonfly moved its head to keep the image of its prey centered on the eye, despite the rotation of its own body. The head movements happened too fast to be a reaction to visual disturbances created by the rotation of the dragonfly’s body, Leonardo says. Instead, the head movements must be planned based on the insect’s predictions about how to stabilize the image of its prey.
Leonardo compares this to something we can relate to. He says that even reaching for a cup of coffee "demands sophisticated information processing" that includes having an internal model of how your arm works, how the muscles and joints are articulated, and the expected mass of the cup. "Articulating a body and moving it through space is a very complicated problem."
Veteran insect-flight researcher Michael Dickinson at Caltech was also impressed. Writing in Current Biology, he quickly sweeps past the obligatory evolutionary language to wax eloquent about the sophistication of dragonfly design:
The first animals to see a cohesive image of the world evolved sometime in the Cambrian, roughly 530 million years ago. We cannot know the exact selective pressures that drove the evolution of eyes, but the ability to detect and track prey was likely one their earliest functions. Many swimming and running animals chase their prey, but there is something particularly wondrous about flying predators that can maneuver deftly in three dimensions. Dragonflies with their sleek bodies, double set of wings, and monstrously large eyes are certainly among the most engaging aerial hunters, and the means by which they catch prey has intrigued biologists and amateurs alike… A recent paper by Mischiati et al. provides new evidence that these creatures hunt using internal models of their prey’s behavior and their own motor actions.
He goes on to describe details so that we can "appreciate the complexity" of these insect hunters’ flight capabilities. Dickinson has also written articles on fruit flies that are sure to delight design lovers, like this one in Caltech’s Engineering & Science, "Come Fly With Me" (PDF). After taking readers on an intellectual thrill ride on the backs of the flies in his flight simulator, his conclusion seems a better match with intelligent design than with Darwinism:
In the end, it’s just a fly. Is such an insignificant little organism really worth all this effort? The natural world is filled with complex things, like immune cells, the human brain, and ecosystems. Although we’ve made great progress in deconstructing life into its constituent parts such as genes and proteins, we have a ways to go before we have a deeper understanding of how elemental components function collectively to create rich behavior. The integrative approach that we are using to study fly flight is an attempt to move beyond reductionism and gain a formal understanding of the workings of a complex entity. The fly seems a reasonable place to start, and if successful, I hope such work will stimulate similar attempts throughout biology. The lessons learned along the way may provide useful insight for engineers and biologists alike. Even if you don’t buy such grand visions, I hope you will at least think before you swat.
Fruit Fly Flipper
With fruit flies on our mind, incredible as it seems Cornell researchers have managed to attach magnets to the backs of these super-miniature flyers. The video at PhysOrgshows scientists playing tricks on the flies, manipulating magnetic fields to make them flip over in mid-air. They wanted to see how fast the flies could right themselves. Bob Yirka writes:
Fruit flies are notoriously good fliers, swatting at them usually results in a miss, and if luck intervenes and a strike is landed, the little bugs right themselves nearly instantaneously. But just how good are they at responding to troubles encountered during flight? That was what the research trio sought to discover.
The answer was thirty milliseconds. In about three or four wingbeats after a somersault, the flies were right-side-up and on their way as if nothing happened. "Overall the researchers found the flies possessed remarkable agility in flight, despite their inherent instability — far superior to anything we humans have devised."
Don’t Forget the Butterflies
As beautifully shown in Illustra’s film Metamorphosis, butterflies are beautiful as well as talented. Imagine designing navigation and flight into an insect weighing less than a gram, able to fly thousands of miles from Canada to Mexico.
In the Darwinian scenario, insects were flying before birds appeared. They are on completely different branches of Darwin’s tree of life, yet their sophistication matches or exceeds the astonishing flight capabilities of birds. Add to that the pterosaurs (reptiles) and bats (mammals) — also superb flyers — and you have four independent instances of skilled aviation in the animal world arising (we are told) by "convergent evolution." If the thought of getting one of them blindly stretches credulity, this is incredulity to the fourth power
Dickinson is right: Think before you swat!