SCHOOL BUSES: In New York City, an aerial photo shows school buses parked before students begin classes. Mark Lennihan/AP/File
STRIPES: A zebra eyes visitors at the zoo in Chinsinau, Moldova. John McConnico/AP/File
SOLAR PANELS: A closeup of a solar panel board is pictured at the Safaricom Base Transmission Station (BTS) in Kajiado, Kenya. Noor Khamis/Reuters
CEMETERIES: A bugler plays taps in Arlington National Cemetery in Arlington, Virginia. Kevil Wolf/AP
FIREWORKS: Fireworks explode over palm trees at the end of an outdoor theatrical performance at Green Park in Tripoli, Libya, in September 2009. Ben Curtis/AP
ARMIES: Women members of the militia, a civilian reserve force under China's military, march past Tiananmen Square during a military parade marking China's 60th anniversary in Beijing, October 2009. Ng Han Guan/AP
MOUNTAINS: Rocks on a mountain appear to be painted in Bluff, Utah. Ed Andrieski/AP/File
WHEAT FIELDS: Three combines harvest a wheat field near Salina, Kan., in June 2005. Jeff Cooper/Salina Journal/AP/File
SYNCHRONIZED SWIMMING: Members of Japan's synchronized swimming team compete during the 2000 Summer Olympics in Australia. Kathy Willens/AP/File
PELOTON: A pack of riders cycle up the Aqua Fresca hill during the men's road race at the UCI Road World Championship in Medrisio, Switzerland in September. Denis Balibouse/Reuters
Zebras are best known for their dramatic stripes, but why they evolved remains uncertain. One popular notion is that stripes make it difficult for predators to single out an individual zebra from the herd, but experimental evidence for this or other ideas has been lacking.
ByCharles Choi, LiveScience Contributor
Zebra stripes may deter bloodsucking insects, perhaps helping explain why zebras evolved their stripes, researchers say.