Tag Archives: insect

Biosciences

How and Why Did Metamorphosis Evolve?

papilio_machaon

Evolution is a truly wondrous thing. It has given us eyes and lots of grey matter [which we still don’t use very well]. It has given us the beautiful tiger and shimmering hues and soaring songs of our birds. It has given us the towering Sequoias, creepy insects, gorgeous ocean-bound creatures and invisible bacteria and viruses. Yet for all its wondrous adaptations one evolutionary invention still seems mysteriously supernatural — metamorphosis.

So, how and why did it evolve? A compelling new theory on the origins of insect metamorphosis by James W. Truman and Lynn M. Riddiford is excerpted below (from a detailed article in Scientific American).

The theory posits that a beneficial mutation around 300 million years ago led to the emergence of metamorphosis in insects:

By combining evidence from the fossil record with studies on insect anatomy and development, biologists have established a plausible narrative about the origin of insect metamorphosis, which they continue to revise as new information surfaces. The earliest insects in Earth’s history did not metamorphose; they hatched from eggs, essentially as miniature adults. Between 280 million and 300 million years ago, however, some insects began to mature a little differently—they hatched in forms that neither looked nor behaved like their adult versions. This shift proved remarkably beneficial: young and old insects were no longer competing for the same resources. Metamorphosis was so successful that, today, as many as 65 percent of all animal species on the planet are metamorphosing insects.

And, there are essentially three types of metamorphosis:

Wingless ametabolous insects, such as silverfish and bristletails, undergo little or no metamorphosis. When they hatch from eggs, they already look like adults, albeit tiny ones, and simply grow larger over time through a series of molts in which they shed their exoskeletons. Hemimetaboly, or incomplete metamorphosis, describes insects such as cockroaches, grasshoppers and dragonflies that hatch as nymphs—miniature versions of their adult forms that gradually develop wings and functional genitals as they molt and grow. Holometaboly, or complete metamorphosis, refers to insects such as beetles, flies, butterflies, moths and bees, which hatch as wormlike larvae that eventually enter a quiescent pupal stage before emerging as adults that look nothing like the larvae.

And, it’s backed by a concrete survival and reproductive advantage:

[T]he enormous numbers of metamorphosing insects on the planet speak for its success as a reproductive strategy. The primary advantage of complete metamorphosis is eliminating competition between the young and old. Larval insects and adult insects occupy very different ecological niches. Whereas caterpillars are busy gorging themselves on leaves, completely disinterested in reproduction, butterflies are flitting from flower to flower in search of nectar and mates. Because larvas and adults do not compete with one another for space or resources, more of each can coexist relative to species in which the young and old live in the same places and eat the same things.

Read the entire article here.

Image: Old World Swallowtail (Papilio machaon). Courtesy: fesoj – Otakárek fenyklový [Papilio machaon]. CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=7263187

Technica

Beware! RoboBee May Be Watching You

History will probably show that humans are the likely cause for the mass disappearance and death of honey bees around the world.

So, while ecologists try to understand why and how to reverse bee death and colony collapse, engineers are busy building alternatives to our once nectar-loving friends. Meet RoboBee, also known as the Micro Air Vehicles Project.

From Scientific American:

We take for granted the effortless flight of insects, thinking nothing of swatting a pesky fly and crushing its wings. But this insect is a model of complexity. After 12 years of work, researchers at the Harvard School of Engineering and Applied Sciences have succeeded in creating a fly-like robot. And in early May, they announced that their tiny RoboBee (yes, it’s called a RoboBee even though it’s based on the mechanics of a fly) took flight. In the future, that could mean big things for everything from disaster relief to colony collapse disorder.

The RoboBee isn’t the only miniature flying robot in existence, but the 80-milligram, quarter-sized robot is certainly one of the smallest. “The motivations are really thinking about this as a platform to drive a host of really challenging open questions and drive new technology and engineering,” says Harvard professor Robert Wood, the engineering team lead for the project.

When Wood and his colleagues first set out to create a robotic fly, there were no off the shelf parts for them to use. “There were no motors small enough, no sensors that could fit on board. The microcontrollers, the microprocessors–everything had to be developed fresh,” says Wood. As a result, the RoboBee project has led to numerous innovations, including vision sensors for the bot, high power density piezoelectric actuators (ceramic strips that expand and contract when exposed to an electrical field), and a new kind of rapid manufacturing that involves layering laser-cut materials that fold like a pop-up book. The actuators assist with the bot’s wing-flapping, while the vision sensors monitor the world in relation to the RoboBee.

“Manufacturing took us quite awhile. Then it was control, how do you design the thing so we can fly it around, and the next one is going to be power, how we develop and integrate power sources,” says Wood. In a paper recently published by Science, the researchers describe the RoboBee’s power quandary: it can fly for just 20 seconds–and that’s while it’s tethered to a power source. “Batteries don’t exist at the size that we would want,” explains Wood. The researchers explain further in the report: ” If we implement on-board power with current technologies, we estimate no more than a few minutes of untethered, powered flight. Long duration power autonomy awaits advances in small, high-energy-density power sources.”

The RoboBees don’t last a particularly long time–Wood says the flight time is “on the order of tens of minutes”–but they can keep flapping their wings long enough for the Harvard researchers to learn everything they need to know from each successive generation of bots. For commercial applications, however, the RoboBees would need to be more durable.

Read the entire article here.

Image courtesy of Micro Air Vehicles Project, Harvard.