Ants indoors: tracing them back to the colony
The workers on your worktop are only the visible part of the colony.
Guide 05
Lasius niger, Monomorium pharaonis
Key points
The black garden ant (Lasius niger) comes indoors in warm weather looking for sugar; the pharaoh ant (Monomorium pharaonis), tiny and amber-coloured, lives inside heated buildings. In both cases, the workers you see are a small share of the colony. A slow-acting bait carried back to the nest is how the queens are reached.
Each worker lays a scent trail that the others follow, which is why ants march in neat lines. Squashing the line or spraying insecticide scatters the ants without touching the nest.
The species changes everything: the black ant usually nests outdoors, under paving or at the foot of a wall; the pharaoh ant nests in wall linings and ducts, with many queens. Spraying a pharaoh ant colony can make it split into several nests.
Spotting signs of ants
- 1A trail of workers running from a crack to something sweet or greasy.
- 2Small heaps of soil or sand at the foot of walls or between paving stones.
- 3Swarms of winged ants on hot, thundery days.
- 4Ants in the sugar bowl, the honey or the pet bowl.
Nuisance level
An indicative guide from our technicians, from 1 (moderate) to 5 (high).
- Health
- 1/5
- Damage
- 1/5
- Breeding
- 3/5
Why act
- Soiled food and worktops.
- Pharaoh ant: may turn up in sensitive places (canteen kitchens, care facilities).
- A nuisance that lasts as long as the nest is untouched.
- Winged ants swarming indoors, very unpleasant for a few days.
Our treatment, in four stages
- 01
Locate
Locate: species identification, lines followed back to entry points, likely nest location.
- 02
Treat
Treat: pest control with slow-acting gel bait placed on the trails, which workers carry back and share with the queens.
- 03
Check
Check: follow-up visit built into the protocol, activity assessed, bait renewed if needed.
- 04
Prevent
Prevent: cracks at thresholds and skirting boards sealed, storage advice, photo report and active vigilance.
Good everyday habits
What you can do to lower the risk of a new infestation.
- Wipe up spilt sugar, honey and juice straight away.
- Store food in containers with lids and don't leave pet food out.
- Don't spray insecticide next to a bait: the ants would abandon it.
- Trim branches touching the walls that act as bridges.
Your questions
Why do we see ants again every spring?
Because the colony, often outdoors, has survived the winter. New workers will keep following the same trail for as long as the queens survive.
Are vinegar or lemon enough?
They mask the trail for a while without reaching the nest. The ants find another way in within days.
How long does a bait take to work?
Allow a few days to two weeks: the bait has to be carried and shared throughout the colony. Seeing more ants on the bait at first is normal.
Ants in your home or your business?
Flat, house, restaurant, shop or office: price including VAT shown before you book, 2-hour window, same-day photo report and advice to lower the risk of a return.