Most people have heard the sound of bees among flowers. Bees live almost everywhere in the world —except the arctic areas. Many kinds of agriculture depend on these small, social insects. Without bees, fruit and nut growers as well as many other farmers would not have a crop. There are more than twenty thousand kinds of bees. But only honey bees make enough honey for people to use. Honey bees are highly organized social insects. They work together in a group called a colony (生物群体). Each colony lives in a hive. It contains one queen bee — she lays all the eggs from which the members of the colony come. Each colony has only a few hundred males, called drones. The majority of all bees in a colony are female workers. Bees even have a special stomach, called a honey stomach. It is used to store sweet fluid that the bees gather from flowers. Bees also have long hairs on their body and legs. These hairs capture pollen (花粉) as bees go from flower to flower. Some of the pollen is taken back to the hive. Some, however, is passed to the next flower. This is how many plants are fertilized. Pollen is the reproductive material of plants. Many important agricultural crops depend on bees for fertilization. Inside their hives, bees store sweet fluid from flowers, called nectar (花蜜), and also pollen. They may even gather nectar from some other kinds of insects. These kinds of nectar are also stored in the hive. Bees have organs that produce a fatty substance called wax. They use wax to build structures in the hive that hold eggs and store honey. Bees make honey through a process. They add liquid from their own mouths to the nectar they have stored in the hive. The liquid breaks down the nectar into sugars. As the honey is stored, it dries. It becomes thicker and darker. Honey can be very thin and light in color or dark and thick. How the honey looks depends on the kinds of flowers used by the bees. Most honey is the easily recognized golden color. Although bees are often thought of as honey-makers, they provide a surprising number of products. Also, their greatest economic value is in fertilizing crops — not in honey. How do bees help plants in fertilization __________.