Identifying ants

Black garden ant

The black garden ant (Lasius niger) is the common one. Workers are 3 to 5 mm long. The nest is outdoors, in lawns, patios and under paving, and a colony can reach about 15,000 workers. They forage indoors for sweet food.

If you see a steady line of ants crossing a kitchen worktop in summer, this is almost always the species. It is a nuisance, not a danger.

Pharaoh ant

The pharaoh ant (Monomorium pharaonis) is much smaller, 1.5 to 2 mm, and nests only inside heated buildings. That means it can be active in any month, not only summer. It is the one to take seriously.

Spraying makes the colony split into several new colonies throughout the building, so a spray makes the problem worse. If you suspect pharaoh ants, do not spray them. See ant control for what a professional does.

Seasons

Black garden ants appear from spring and are busiest in summer. Flying-ant days fall in July and August. Pharaoh ants are not seasonal, because they live indoors in the warmth. An ant trail in the kitchen in January is more likely to be pharaoh ants than garden ants.

Flying ants

Flying ants are not a separate species. They are the reproductive males and young queens of ordinary ants, on a nuptial flight. This usually happens on a warm, humid day in July or August, and many colonies fly on the same day.

They can appear in large numbers around windows and lights. A single flying day is normal. Repeated emergence from the same spot indoors suggests a nest in the building.

Where the nest is

Outdoor nests are in lawns, patios and under paving. Indoor nests, which means pharaoh ants, are inside heated buildings, often in warm wall cavities, under floors or near hot pipes. Follow the trail back to where the ants come from. A technician finds the nest during a survey, where possible.

What ants are not

Ants are often confused with other small insects. Flying ants look like winged termites, but winged termites are not a UK house pest. If you cannot tell, a close photograph helps a technician name it quickly, which saves paying for the wrong treatment.

How to tell which you have

Use this quick check:

• Size: 3 to 5 mm points to black garden ants; 1.5 to 2 mm points to pharaoh ants.
• Where they come from: a trail from outdoors fits garden ants; ants appearing inside warm rooms in any season fit pharaoh ants.
• When: a mass of winged ants in July or August is a flying ant day.

If you are unsure, photograph the ants next to a coin and send it to a technician. Naming the species decides the treatment. Once you know, see the DIY guide or the cost guide.