Honey bees are social insects that live in colonies. A bee colony consists of a queen bee, male drones（雄蜂） and thousands of female worker bees. Each colony also contains eggs and immature （不成熟的 [.imә'tjuә] ）bees in various（[ˈveriəs]）stages of development. The number of bees within a colony depends on seasonal changes. A colony's population increases during the warm seasons and decreases during colder seasons.
In recent years, many bee colonies have collapsed（倒塌 瓦解） or disappeared. A bee colony collapse occurs when a majority of the bees in a colony disappear and **leave behind（遗留 留下） **the queen. Some beekeepers have reported losing 30 to 90 percent of their colonies. This loss of bee colonies can cause significant（显著的） problems for farmers who depend on them to pollinate their crops. In some parts of the world, a shortage（短缺） of bees has increased the cost of renting bees by up to 20%.
There are several possible causes for bee colony collapse. One possible cause is the use of new pesticides（杀虫剂）. Other possible causes include infections from viruses（[ˈvaɪrəs]）, genetic factors（生殖因素）, and malnutrition（营养不良[.mælnju:'triʃәn]）. Changing weather patterns may also play a role as summers get hotter and winters get colder. These changes in weather may weaken the bees, making it more difficult for them to fight infections.
Whatever the cause of colony collapse, it's important to understand that many parts of our world are interdependent（相互依赖的）. Changes that affect one species may have serious effects on other species. A change to our environment can start a chain of events that is difficult to predict. In any complex system such as the Earth's environment, small changes can have unforeseen consequences （结果）.The danger of unforeseen consequences is something we all need to understand better.