Typical worker ants are 3-4mm long of a brown/black colour with elbowed antennae and biting mouthparts. The queen tends to be much larger at about 10mm.
Garden Ants usually nest outdoors in lawns, flower beds, beneath paving flags and at the base of walls. Premises are usually invaded by worker ants foraging for food, especially sweet foods. During summer, winged females (Queens) and males leave the nest on one or two warm afternoons and take flight. During this flight, which may only last for 2- 3 hours, the ants mate. The formation of a new colony starts with a mated winged female digging into the earth to overwinter and start a new colony in the spring.
If possible, trace the trail of worker ants to the nest. If the nest can be exposed, and it is safe to do so, apply an insect powder labelled for that use. If it is not possible to trace the nest, use a residual insecticidal spray to treat outside the building. Special attention should be paid to likely entry points such as door frames, air bricks and waste pipes to create an insecticidal barrier. In addition, use of gels and liquid feeding baits can help with longer-term control.