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Next time you go traipsing in the woods and a fly buzzes around you, don't swat it. You may be contributing to the eradication of one of the islands' most illustrious insect species -- the Hawaiian picture-wings. Mutating flies unravel
mysteries of evolutionBy Janine Tully
Star-BulletinThe tiny flies, less than a quarter of an inch long, have created a stir among entomologists for their ability to mutate into thousands of species.
Scientists believe that as many as 1,000 picture-wing species may exist in Hawaii, each one adapted not only to a particular island, but also to a specific habitat -- ranging from dry areas to rain forests and marshes. Picture-wings are mostly seen in rain forests at mid-level, however.
"Just the sheer numbers set them apart," said David Foote, a researcher with the Pacific Island Ecosystems Research Center of the U.S. Geological Survey.
"If you take a butterfly net and sweep it back and forth in a mainland forest you'll get lots of different insects. In Hawaii you'll get mostly picture-wings because of the multitude of species," Foote said.
Some picture-wings are dwindling, however, because of habitat degradation caused by feral animals, alien weeds, ants and yellowjackets, as well as pesticides and forest fires. Two species exist in such small numbers that a hurricane or landslide could wipe them out.
The U.S. Fish and Wildlife Service has requested that 12 of the most at-risk fly species be added to the endangered species list.
"Over the years, Hawaiian picture-wings have provided the scientific community with extraordinary knowledge about evolutionary biology," said Anne Badgley, regional director for Fish and Wildlife. "It's sad that these species are now in need of protection."Said Foote: "Picture-wings are used over and over in biology textbooks to showcase evolution in Hawaii and we don't want to put a footnote in those textbooks. They help unravel the mystery of how new species form. And they have undergone such dramatic diversification in Hawaii that they provide a model for understanding evolution."
Members of the Drosophilidae family, picture-wings have been studied by local scientists for decades, leading them to test new evolutionary theories.
"The main thing that has created the scientific interest is the amazing evolution these species have undergone, possibly, in the last seven million years," said Wildlife Service entomologist Mike Richardson.
Just like animals on the Galapagos Islands that adapted to their environment and evolved to fit different niches, so have picture-wings, except ten-fold, Richardson said.
"They have evolved into hundreds or perhaps thousands of species taking advantage of hundreds of different natural ecosystems," he added.
Besides being valued for their evolutionary prowess, picture-wings help scientists determine the health of Hawaii's forests.
Also, unlike the Mediterranean fruit fly that breeds on fruits still on trees, causing agricultural damage, picture-wings breed on rotting fruits and native rotting vegetation such as olapa and ohawai. They feed on bacteria produced by their host.
Picture-wings are prettier than other flies, say scientists, with emerald-green bodies and translucent wings with black blotches or stripes, depending on the species. They have been called the "birds of paradise" of the insect world because of their elaborate courtship display and fierce defense of territory.
Six of the picture-wings proposed as endangered species are found on Oahu, three on the Big Island, and one each on Molokai, Kauai and Maui.
Maui's sphinx moth and the Hawaiian snail are two insects that have been placed on the endangered species list. Richardson doesn't expect that an agency moratorium on critical habitat designations will slow down the process of listing the flies as endangered.
"There's money available from last fiscal year for species we consider high priority," he said. "Picture-wings are the most illustrious examples of insect evolution in the world."