Ants
The Black Ant allthough they prefer to nest outside, can become a nuisance when the foraging workers enter buildings in search of food. They follow well defined trails and will cluster around food sources.
In late spring the new queens and the fertile males are able to fly and mating takes place on the wing. This can be a spectacular and often alarming sight involving hundreds of ants. this swarming usually only lasts a couple of hours. Once mating has finished the males die and the females shed their wings and go off to start new colonies. A nest can survive for several years.
If the nest is accessible any insecticide cleared for use on ants will kill the colony. However the nest is often well inside the fabric of a building and inaccessible. in this case residual crawling insect spray can be applied to points of entry such as doors, windows, ventilators and around ducting carrying pipework ect. Insecticide should also be applied along known runs and wall floor junctions. Poison baits may be used that are taken back to the nest by the foraging workers. I personally do not use insecticidal dusts. When used outside they soon become weathered and inactive, and when used indoors besides looking unsightly, there is always the greater risk of contamination of food stuffs especially when used in kitchens.
Flying ants can be dealt with using a normal fly spray. 
Ants entering from outside may be controled by simply proofing cracks and entry points using mastic or something similar. Any food spillage should be cleared and potential food sources protected
