Zebra stripes discourage horseflies from biting - The State Column

The mystery of zebra stripes and horseflies has been revealed. A study published Thursday in the Journal of Experimental Biology provides evidence that zebra stripes may discourage horseflies from biting. Prior to the study, researchers thought the zebra stripes were designed to confuse predators. While this may still be the case, the deterring impact of zebra stripes appears to be aimed primarily at horseflies.

“We demonstrate that a zebra-striped horse model attracts far fewer horseflies (tabanids) than either homogeneous black, brown, grey or white equivalents,” the researchers write in the study’s abstract.

Horseflies, which can carry diseases and distract their victim from feeding or drinking, are unwelcome visitors to zebras and other animals that graze. According to Gábor Horváth, one of the study’s authors, horseflies are attracted to horizontally polarized light because sunlight that reflects off of water is horizontally polarized. When horseflies and other aquatic insects discover water they can mate and lay eggs. The female variety of horseflies, however, are also attracted to linearly polarized light that reflects from the hides of their victims.

Zebra embryos, which start out with dark skin and develop white stripes before being born, raised an important question with the researchers. Did the zebra develop stripes over time in order to deter disease-carrying horseflies and other insects?

In order to determine whether a zebra’s stripes really deter horseflies, the team traveled to Budapest and set up camp at a horse farm with plenty of horseflies. The team attempted to attract horseflies using black and white striped patterns that varied in width. Using oil and glue to capture the horseflies, the narrowest black and white striped strips attracted the fewest insects.

The team of researchers also measured the attractiveness of white, dark and striped horses to horseflies. Although the team expected the results to reveal that white horses were the least attractive, they found that the striped version captured the least number of horse flies.

“We created an experimental set-up where we painted the different patterns onto boards,” researcher Susanne Akesson of Lund University posited to BBC Nature. “We put insect glue on the boards and counted the number of flies that each one attracted,” Ms. Akesson added.

While researchers have not eliminated the possibility that zebra stripes might have benefits besides the deterrence of horseflies, they believe that a zebra’s striped coat pattern is a key factor in repelling disease-carrying insects.

“We believe that escaping biting flies, which are annoying to their hosts and transmit lethal diseases, would be a very important selection factor, which may have a much stronger effect than the benefits of striped coat patterns suggested previously,” Ms. Akesson told LiveScience.

Until recently, zebra stripes were thought to be primarily designed for camouflage in the wild. Scientists believe that zebra stripes act as camouflage in two ways. First, the wavy stripes help the zebras blend into the grasses around them. A lion, one of the animal’s natural predators, is colorblind which means that it is unable to tell the difference between the grass and the zebra. Second, scientists believe that a zebra is able to use its stripes to blend in with other zebras in a herd. When a predator spots a herd of zebras, it sees a mass of black and white stripes instead of individual zebras. Although these uses for zebra stripes are still relevant, the study’s authors believe that they are no longer the primary reasons that a zebra has stripes.

“We conclude that zebras have evolved a coat pattern in which the stripes are narrow enough to ensure minimum attractiveness to tabanid flies,” the team of researchers posited in the Journal of Experimental Biology, adding that “the selection pressure for striped coat patterns as a response to blood-sucking dipteran parasites is probably high in this region [Africa].”

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Atlantis docks with space station one final time - Houston Chronicle

Atlantis has docked with the International Space Station.

At 9:08 a.m. today, the shuttle flew near the space station and performed a 360-degree back flip in space, allowing astronauts aboard the orbiting laboratory to photograph the belly of the shuttle.

These images will be sent to imagery experts on the ground who will ensure that the shuttle belly's heat shield tiles were not significantly damaged during Friday's launch.

After the back-flip maneuver, commander Chris Ferguson guided Atlantis toward the station and docked shortly after 10 a.m.

And with that, Atlantis' crew began transferring all that cargo they brought to orbit.

Atlantis spent a nearly flawless first full day in orbit on Saturday, with the space shuttle's crew inspecting the vehicle to ensure it sustained no significant damage during launch.

Although a final assessment of the shuttle's heat shield won't be made until later this week, upon first appearance it looks to be in good condition. During the last mission of the space shuttle program the vehicle, overall, is behaving very well, NASA officials said.

"I couldn't be happier with where we are right now," said LeRoy Cain, chairman of the mission management team.

The four astronauts aboard Atlantis — Ferguson, pilot Doug Hurley, and mission specialists Sandra Magnus and Rex Walheim — spent a busy Saturday in space using a robotic arm with a camera attached to inspect the shuttle's nose and the leading edges of its wings for impact damage.

It's been more than two decades since a shuttle has flown with so few crew members, and there are typically six or seven astronauts on the vehicle to assist with these inspections.

"We normally do have some more hands on board, but I'm happy to report that our four-person crew is staying well ahead of the timeline," Cain said. "And that's saying a lot for flight day two."

NASA assigned just four astronauts to the flight because it wanted to pack the spacecraft with as many supplies as possible for a delivery run to the International Space Station.

Significantly, Atlantis will deliver a year's worth of food to the six space station crew members.

eric.berger@chron.com

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President Obama not giving up on big debt deal - Atlanta Journal Constitution

By LAURIE KELLMAN

The Associated Press

WASHINGTON — President Barack Obama hasn't given up on getting congressional leaders to accept a $4 trillion debt reduction deal that Republicans have rejected for its tax increases and Democrats dislike for its cuts to programs for seniors and the poor, administration officials said hours before talks resumed Sunday.

President Barack Obama crosses the South Lawn of the White House in Washington to board Marine One Saturday, July 9, 2011. Obama is headed to Camp David, the Presidential retreat in Catoctin Mountains. (AP Photo/Carolyn Kaster)
In this photo provided by CBS News, U.S. Treasury Secretary Timothy Geithner talks about the debt crisis on CBS's "Face the Nation" in Washington Sunday, July 10, 2011. Geithner said Sunday that the Obama administration wants to seek "the biggest deal possible" on debt reduction. His comments followed word from GOP congressional leaders Sunday that the White House's $4 trillion package was off the table. (AP Photo/CBS News, Chris Usher)
FILE - In this July 7, 2011, file photo President Barack Obama and House Speaker John Boehner of Ohio meet with Congressional leadership in the Cabinet Room of the White House in Washington to discuss the debt. A debt-busting deal on the scale that Obama and Boehner are seeking all but guarantees Medicare beneficiaries would feel part of the pain. Some working-age people and their families could also be on the hook, if the deal ultimately curtails the tax break for employer-provided health insurance. (AP Photo/Pablo Martinez Monsivais, File)
In this photo provided by CBS News, U.S. Treasury Secretary Timothy Geithner talks about the debt crisis on CBS's "Face the Nation" in Washington Sunday, July 10, 2011. Geithner said Sunday that the Obama administration wants to seek "the biggest deal possible" on debt reduction. His comments followed word from GOP congressional leaders Sunday that the White House's $4 trillion package was off the table. (AP Photo/CBS News, Chris Usher)

"He's not someone to walk away from a tough fight," presidential chief of staff William Daley said. "Everyone agrees that a number around $4 trillion is the number that will ... make a serious dent in our deficit."

But House and Senate Republican leaders now say the largest of three proposals under consideration would not pass the GOP-led House because of its tax increases, an abrupt shift in negotiation over the terms of raising the nation's debt ceiling before an Aug. 2 deadline.

House Speaker John Boehner, R-Ohio, announced late Saturday that he was rejecting that proposal. Heading into the talks at 6 p.m. EDT, the top Senate Republican, Mitch McConnell of Kentucky, suggested the deal was dead.

"I think it is," McConnell said. Raising taxes amid 9.2 percent unemployment, he added, "is a terrible idea. It's a job killer."

The back-and-forth on the Sunday morning talk shows came hours before Obama and eight lawmakers of both parties were to convene at the White House over a plan to raise the nation's borrowing capacity from $14.3 trillion before next month's deadline, when administration officials say the nation would default on its debts.

Republicans have demanded that any plan to raise the borrowing limit be coupled with massive spending cuts to lighten the burden of government on the struggling economy. Higher taxes, Republicans have said from the start, are deal-killers if not offset elsewhere.

But Obama has a long way to go to satisfy lawmakers in his own party, too. Many Democrats are unnerved by the president's $4 trillion proposal because of its changes to Medicare and Medicaid.

Political pain is part of the deal, too, and should be worth bearing, Daley said, adding that Obama was calling on lawmakers to "step up and be leaders."

He cast Obama as uninterested, for now, in two more modest proposals to raise the debt limit for a shorter time, in exchange for smaller spending cuts. But Daley and Treasury Secretary Timothy Geithner used rhetoric that appeared to acknowledge the prospects for the $4 trillion deal could be in doubt.

"We're going to try to get the biggest deal possible," Geithner said.

He cautioned that a package about half the size of the one Obama prefers would be equally tough to negotiate because it, too, could require hundreds of billions in new tax revenue.

Expectations for Sunday's meeting took an abrupt turn after Boehner informed Obama that a package of about $2 trillion identified but not agreed to by bipartisan negotiators was more realistic.

In a statement, Boehner said: "Despite good-faith efforts to find common ground, the White House will not pursue a bigger debt reduction agreement without tax hikes."

A bipartisan group of lawmakers led by Vice President Joe Biden had already identified, but not signed off on, about $2 trillion in deficit reductions, most accomplished through spending cuts.

"I believe the best approach may be to focus on producing a smaller measure, based on the cuts identified in the Biden-led negotiations, that still meets our call for spending reforms and cuts greater than the amount of any debt limit increase," Boehner said.

After holding a secret meeting with Boehner last weekend, Obama and aides said they believed an even bigger figure was attainable if both parties made politically painful, but potentially historic, choices.

A Republican official familiar with the discussions said taxes and the major health and retirement entitlement programs continued to be sticking points.

Obama wanted Republicans to accept closing some corporate tax loopholes and subsidies to corporations, ending a tax friendly inventory accounting system for businesses, as well as reducing the value of tax deductions for wealthy taxpayers.

A senior administration official said the discussion on taxes broke down over the administration's desire to have the wealthy pick up a bigger share of the tax revenue load than Republicans were willing to accept.

The official, speaking on the condition of anonymity because of the sensitivity of the negotiations, said the $2 trillion to $2.4 trillion in deficit reduction identified by the Biden-led negotiations remains under negotiation and will also require some new tax revenue of up to $400 billion.

Daley was on ABC's "This Week," McConnell appeared on "Fox News Sunday" and Geithner was interviewed on NBC's "Meet the Press" and CBS' "Face the Nation."

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Associated Press writer Jim Kuhnhenn contributed to this report.

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July 10, 2011 12:11 PM EDT

Copyright 2011, The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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