Tuesday, 4 January 2011

Johnald's Fantastical Daily Link Splurge

Johnald's Fantastical Daily Link Splurge

Amazing World of Insect-Wing Color Discovered

Posted: 03 Jan 2011 01:41 PM PST

A closer look at seemingly drab, transparent insect wings has revealed realms of previously unappreciated color, visible to the naked eye yet overlooked for centuries.

Until now, the wing colors of many flies and wasps were dismissed as random iridescence. But they may be as distinctive and marvelous as the much-studied, much-celebrated wings of butterflies and beetles.

"Given favorable light conditions, they display a world of brightly patterned wings that are apparently unnoticed by contemporary biologists," wrote researchers led by University of Lund entomologists Ekaterina Shevtsova and Christer Hansson in a December 3 Proceedings of the National Academy of Sciences paper.


Wasp and fly wings are made from two compressed layers of transparent chitin, with light bouncing off both layers and mixing to produce color. The same is true of oil slicks and soap bubbles, and scientists considered transparent wing coloration "a soap bubble iridescence effect, with randomly changing colors flashing over the wing surface," wrote the researchers.

Instead, the researchers found that surface variations in chitin filtered out the iridescence. Remaining colors proved to be stable, and were visible from almost any angle. They differed consistently between species and sex.

Generations of biologists seem to have missed this partly because they didn't look for it, and partly because the colors are most evident against a dark background. Against a white background, they're invisible — which is exactly how most entomologists study transparent wings.

"You hold the wing up against the light, so you can see the veins," said study co-author Daniel Janzen, an evolutionary ecologist at the University of Pennsylvania. "If you're looking through a microscope, you try to get a clear view behind the wing. It's the antithesis of getting wing color."

The researchers studied wings under microscopes, against black backgrounds. But once Janzen, who breeds wasps for his research on caterpillar-parasite symbioses, started to look, colors could be seen by the naked eye as wings passed over insects' black bodies.

"They flash like little diamonds," he said.

The researchers think the coloration has specific functions, particularly for mating, just as it does in butterflies and beetles and other insects with better-appreciated markings.

The patterns will also help scientists distinguish between species difficult to differentiate in other ways. Already the researchers used transparent wing colors to identify three new species of wasp.

According to Janzen, at least a dozen other orders of insects, spanning dragonflies and cockroaches and grasshoppers, have transparent wings likely to be as colorful as those of wasps and flies.

"I envision taxonomists going back to their animals, and looking at them in a new light," he said. "It's like discovering a whole new piece of the animal."

Images: 1) Fruit fly against white and black backgrounds./PNAS. 2) Patterns in fly wings (top half) and wasp wings (bottom half)./PNAS. 3) Composite image of fly against white and black bacgrounds./PNAS. The images are all true-color, modified only by a 10 percent increase in color saturation.

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Citation: "Stable structural color patterns displayed on transparent insect wings." By Ekaterina Shevtsovaa, Christer Hanssona, Daniel H. Janzen, and Jostein Kjærandsend. Proceedings of the National Academy of Sciences, Vol. 108 No. 1, January 4, 2011.

Elusive Meteor Shower and Solar Eclipse to Ring in 2011

Posted: 03 Jan 2011 01:08 PM PST

The new year opens up with the annual Quadrantid Meteor Shower, one of the most impressive — but least observed — meteor showers of the year.

The shower is expected to peak sometime between 3 p.m. EST on Jan. 3 and 1 a.m. EST on Jan. 4. Observers in North America should look for shooting stars emanating from low on the northwestern horizon as soon as it gets dark, or towards the northeast just before dawn.

The Quadrantids are a major shower, with this year's peak expected to display more than 100 meteors per hour. But almost no one ever sees it, partly because of typical January weather and partly because the peak lasts a few hours at most. Tonight's skies will be moon-free, however, so if it's clear, it will be dark.

The shower's source was a mystery until 2003, when SETI astronomer Peter Jenniskens found evidence that the meteoroids come from a broken comet called 2003 EH1. As the Earth passes through the dead comet's orbit, bits of dust and debris in the object's wake blaze through the atmosphere. Earth's orbit intersects the comet's orbit at a right angle, meaning we move quickly through the debris stream. That's probably why the shower's peak is so brief.

As a bonus, viewers in Europe, northern Africa, the Middle East and parts of Asia will see a partial solar eclipse the morning of Jan. 4. This is the first year in three years when a total solar eclipse won't be visible from somewhere in the world, and the last chance to see a partial eclipse from Europe until 2015. In western Europe, up to 86 percent of the solar disk will be obscured by the moon at dawn, producing a beautiful crescent sunrise.

NASA provides a timeline and viewing tips. If you're not in viewing range, you can watch online: The eclipse will be webcast from AstronomyLive.com, the University of Barcelona and Bareket Observatory in Israel.

Image: flickr/Adcuz

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Parasites Make Caterpillars Glow to Repel Predators

Posted: 03 Jan 2011 12:00 PM PST

Parasitic worms may be saving their own little hides when they induce the caterpillars they infest to glow a little and blush a furious red.

As the parasitic nematode Heterorhabditis bacteriophora infects caterpillars of the greater wax moth, the normally pale caterpillars temporarily bioluminesce and also turn persistently pink-red.

In outdoor taste tests with 16 European robins, birds overall preferred uninfected waxmoth caterpillars to ones that had been infected for at least three days. By the seventh day of infection, odd-colored caterpillars barely even got tentatively picked up by the birds, Fenton and his colleagues report in an upcoming paper in Animal Behaviour.

"I think the cool thing is that it's the first example, to our knowledge, of a parasite manipulating its host to avoid being eaten," says Andy Fenton of the University of Liverpool in England.


It's to the parasite's advantage not to be eaten, Fenton explains, because these nematodes don't infect vertebrates. So if a bird happens to eat a parasitized caterpillar, it's bye-bye wormy.

Biologists have already uncovered weird examples of the opposite approach, in which other parasites change the appearance or behavior of hosts in ways that attract predators. Ants infected with the parasitic Dicrocoelium dendriticum worm, for example, crawl up grass blades until a grazing cow or sheep inadvertently scoops them up with a mouthful of forage. This worm does infect grazers and thus sacrifices its current host to the next one.

Young nematodes of the species in the new study search through soil for larvae of a range of flies, beetles, butterflies and moths. Slipping into victims through the mouth, breathing holes or anus, the nematodes release live-in luminescent bacteria that reduce the host's innards to a nutritious broth for both the nematodes and their microbial passengers.

Whether the parasites benefit in some way from their hosts' reddening and weak, transient glow — which is undetectable to the human eye in daylight but easily visible in a darkened room — has inspired considerable speculation, Fenton says. Researchers have mused about whether the color change may be just a side effect of reducing the buildup of highly reactive forms of oxygen. As far as he knows, Fenton says, his is the first test of the warning-color idea with real birds and caterpillars and parasites.

"This is an old idea but a fun one," comments Richard ffrench-Constant of the University of Exeter in England, who has studied the nematode but wasn't involved in the new research.

Studying parasite manipulations does offer the immediate fascination of the "gross and riveting," Fenton acknowledges. But the parasite takeovers also give evolutionary biologists some extreme examples of evolution acting on the genes of one species, the parasite, as the genes change the body of a completely different species, the host.

Image: Peggy Greb, USDA Agricultural Research Service, Bugwood.org

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How to Capture the Sun in a Beer Can

Posted: 03 Jan 2011 10:45 AM PST

This sun-streaked image comes from the easiest, yet most time-intensive DIY astrophotography project ever: solargraphy.

Solargraphs trace the seasons by exposing a sheet of photosensitive paper to sunlight for up to a year. The bright arches in this image mark the sun's path across the sky in Middleburg, the Netherlands, from the summer solstice to the winter solstice.

Amateur astronomer and photographer Jan Koeman slipped a piece of photographic paper into an empty beer can, poked a hole in the can with a pin, and suspended the makeshift camera in the garden from July to December. The sun's daily tracks, high in the summer and low in the winter, were etched onto the paper. Sometimes the tracks were interrupted by clouds, and some rainy days are missing entirely.

"Solargraphy is very basic photography. And it is a combination of art, science and chemistry," Koeman said in an e-mail to Wired.com. "Everyone can do it, and the camera (empty tin) is for free!"

Images: Jan Koeman

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