If you've spotted tiny yellow-brown ants — around 2mm long — trailing along worktops, around sinks or in bathrooms during summer, they're almost certainly pharaoh ants (Monomorium pharaonis), not the familiar black garden ant. They're a tropical species that lives entirely indoors in heated UK buildings, and they're the single hardest ant we deal with.
Why they're a serious problem
- Multiple queens per colony — killing workers does nothing
- Colonies fragment ('bud') when stressed by sprays, turning one nest into several
- They nest in wall cavities, behind tiles, in plug sockets and inside appliances
- They're known mechanical vectors of pathogens including salmonella and staphylococcus — a notifiable concern in care homes and hospitals
Why insect sprays are the worst thing you can do
A repellent spray scatters the colony into the building fabric and triggers budding. We've taken on jobs where a well-meaning DIY spray turned one flat's problem into a whole-block infestation within three months.
What actually works
Specialist non-repellent gel baits containing an insect growth regulator, placed at trail points and replenished over 6–12 weeks. The workers carry the bait back to every queen, sterilising the colony before it collapses. In blocks of flats, neighbouring units almost always need treating at the same time — we coordinate with managing agents across Hertfordshire and North London to do exactly that.