In British species of ant there are three distinct castes, or class; worker, male, and queen. In some tropical species there is also a fourth caste; soldier. Soldiers are large workers, often with enlarged heads containing strong jaw muscles, whose primary role is the defence of the nest. Some soldiers heads are so enlarged that they almost look like heads on legs.
The worker ant shown above is Lasius niger, the common black garden ant, which can be found in many places in the UK, and throughout Europe. As its caste name suggests these ants are the ones that carry out the daily tasks of the colony such as foraging, brood care, nest repair and defence, and taking care of the queen. Although all worker ants are female they generally do not lay eggs, however, in certain cases they do lay eggs but these are normally used as food. If the worker-laid eggs, which are unfertilised, are allowed to develop they will produce male ants; this may be allowed to happen if the queen of the colony has died. In this case the colony is doomed as there is no queen to produce more workers. By the act of a worker laying unfertilised eggs and thereby producing males; at least the dying colony's genes may be passed on to a virgin queen elsewhere.
Male ants, as shown in the picture left (winged) quite often the smaller of the three castes, have only one role in life - to inseminate a virgin queen during the mating flight. Once they have performed this task they die within a few days. Male ants are produced from unfertilised eggs normally laid by the queen. Their antennae are not jointed as are the other castes, though they have perhaps the best eyesight of all casts.