Ants are insects whose social life is highly organized, comparable only to that of honey bees or termites. Ants are considered social insects because they live in organized colonies and formcomplex societies. They are generally composed of three castes: the queen, the drones and theworkers. Each caste has its own specific morphology and carries out specific tasks within thecommunity. Colony life has many advantages, one of the most important    17     increased protectionfor the entire group.       Generally, each ant colony has only one queen. She spends her life laying eggs. There are alsofemale worker ants that do not reproduce, instead carrying out a number of other tasks: foragingfor food, caring for the queen and her brood, building galleries, maintaining the nest, anddefending the anthill. The only purpose that drones serve is to fertilize queens, and drones are onlyfound inside the colony for short periods of time. Shortly after    18   , drones die.       Ants generally mate in the air. The queen’s abdomen contains a small spherical receptaclecalled a spermatheca, which receives spermatozoa during conception. The spermatheca producesnutrients that keep the semen alive for several years, allowing the queen to lay thousands of eggswithout mating with another    19    .       Once she is in her new home, the queen lays her first eggs. She cares for the first broodherself, feeding them from her own reserves. The first adult workers are very small. This firstgeneration of workers, and all future generations, are in charge of all the work in the anthill. Ants communicate with one another by brushing their antennae together, through sound andespecially through odorous chemical substances called pheromones. These chemical particles,released by both workers and the queen, regulate sexual and social behaviour within a species. Insome species, if an old queen is sick, she releases    20    that cause workers to feed certain larvae inorder to produce a new queen who will take over when the old queen dies.17. (A) being (B) is (C) has been (D) to be