Malta has a long tradition of bee-keeping and this tradition is still going strong although lately it has passed through difficult times. Bees are kept in special boxes with partitions for the queen bee and for the other members of the community. A collection of such boxes is called an apiary. Apiaries require an ample supply of nectar and pollen and are usually kept where nectar-producing plants such as clover, citrus trees, wild thyme or eucalyptus are abundant. Apiaries may consist of any number of hives, depending on the means of the beekeeper and the flower resources available. Commercial beekeepers who make their entire living from bees often keep a large number of hives to make their business viable. Boxes hold about ten wood-bound comb frames. Worker bees are the most numerous members of the colony. A healthy colony may contain 80,000 worker bees or more at its peak growth in early summer. Workers build and maintain the nest and care for the brood. They build the nest from wax secreted from glands in their abdomen. The hexagonal cells, or compartments, constructed by the workers are arranged in a latticework known as the comb. The cells of the comb provide the internal structure of the nest and are used for storage of the developing young bees and all the provisions used by the colony. Comb used for storage of honey is called honeycomb. Workers leave the hive to gather nectar, pollen, water, and propolis, a gummy substance used to seal and caulk the exterior of the nest. They convert the nectar to honey, clean the comb, and feed the larvae, drones, and the queen. They also ventilate the nest and when necessary, defend the colony with their stings. Workers do not mate and therefore cannot produce fertile eggs. They occasionally lay infertile eggs, which give rise to drones.