Where Have All the Bees Gone？
？？ Scientists who study insectshave a real mystery on their hands. All across the country, honeybees areleaving their hives and never returning. Researchers call this phenomenoncolony-collapse disorder. According to surveys of bee keepers across thecountry,25 t0 40 percent of the honeybees in the Unit- ed States have vanishedfrom their h？？ives since last fall. So far,no one can explain why.
？？ Colony collapse is a seriousconcern because bees play an important role in the productton of aboutone-third of the foods we eat. As they feed, honeybees spread pollen fromflower to flower. Without this process,a plant can't produce seeds or fruits.
？？ Now,a group of scientists andbeekeepers have teamed up to try to figure out what's causing the alarmingcollapse of so many colonies. By sharing their expertise in honeybee behavior,health, and nu- trition, team members hope to find out what's contributing tothe decline and to prevent bee？？ disappear- ance in the future.
？？ It could be that disease iscausing the disappearance of the bees. To explore that possibility,Jay Evans,aresearcher at the United States Department of Agriculture (USDA) Bee ResearchLaboratory,examines bees taken from colonies that are collapsing. "We knowwhat a healthy bee should look like on th？？e inside,and we can look for physicalsigns of disease," he says. And bees from collapsing colonies don't lookvery healthy. "Their stom？？achs are worn down, compared to t？？he stomachs ofhealthy bees, " Evans says. It may be that a par- asite is damaging thebees digestive organs. Their immune systems may not be working as they should.Moreo- ver,they have high levels of bacteria inside their bodies.？？
？？ Another cause ofcolony-collapse disorder may be certain chemicals that farmers apply to killun- wanted insects on crops,says Jerry Hayes, chief bee inspector for theFlorida Department of Agricul- ture. Some studies, he says, suggest that acertain type of insecticide affects the honeybee's nervous system (whichincludes the brain) and memory. "It seems like honeybees are going out andgetting confused about where to go and what to do," he says.
？？ If it turns out that adisease is contributing to colony collapse, bees genes could explain why somecolonies have collapsed and others have not. In any group of bees there aremany different kinds of ge？？nes. The more dif- ferent genes a group has, thehigher the group's genetic diversity. So far scientists haven't determined therole of genetic diversity in colony collapse, but it's a promising theory, saysEvans.
What is the mystery that researchers find hard to explain？？？

A. Honeybees are flying all across the country
B. 25-40 percent of the honeybees in the US have died
C. Honeybees are leaving their hives and do not return
D. Honeybee hives are in disorder