Why your neighbour's ants flew and yours didn't

Someone two doors down spent Tuesday afternoon shutting their windows and posting about it. You went out, looked at your lawn, got nothing. Same street, same weather, near-certainly the same species living under both of you.

It is the most common question people ask about flying ants, and the answer turns out to be more interesting than bad luck.

The Royal Society of Biology ran a public flying-ant survey across 2012, 2013 and 2014, and the results are still the best data anyone has on this. It is British data, gathered at a scale nobody has matched elsewhere, but what it measures is how colonies behave rather than anything peculiar to Britain. Two findings matter here.

Flying ants were reported somewhere in the UK on 96% of days between the start of June and the start of September. And there was no meaningful geographical coordination between them.

That second one is your answer. One garden gets its flight, the garden two streets over gets one a fortnight later, and both of those are ordinary. Nothing is being broadcast across the neighbourhood.

Colonies read the weather from underground, which is the bit that tends to get skipped over.

Boomsma and Leusink's 1981 work on four European species put forward the idea that queens go up when air temperature has caught up with the temperature of the soil the nest is sitting in. Whether or not that holds exactly, the shape of it looks right: what the colony responds to is a relationship between conditions down where the brood is and conditions up in the air.

And soil temperature is a hyper-local number. A nest under a south-facing paving slab is in a different world from one four metres away under a shaded lawn with a hedge over it. The slab takes heat all morning and gives it back into the evening; the lawn never really gets going. Same afternoon, same air temperature, and the two colonies are nowhere near the same state of readiness.

Which is the awkward part for anything calling itself a forecast. The weather over your street is genuinely shared. The thing the ants are keyed to sits a few centimetres down and is private to each nest.

Support for that turned up this year from an unlikely direction.

A team in Barcelona went through swifts killed in bird strikes at the airport, picked through the stomach contents of 72 carcasses, and found ant remains in 31 of them across 16 species. The study was about phenology, using the birds as an accidental record of when flights had happened. But they also checked the obvious thing: on the days the swifts had been eating ants, was the weather different from the days they hadn't?

It wasn't. Temperature, humidity, wind speed and rainfall showed no significant difference between the two sets of days. Their own reading is that colony-level factors are what drive the timing.

That is a Mediterranean species list reached by a very indirect route, and I would not lean on it hard. It is worth having as a second and quite separate line of evidence arriving where your street already pointed.

A colony cannot fly until it can afford to.

Winged queens and males are expensive to produce, and a colony has to reach a certain size and age before it makes any at all, which for many common species means a few years of turning out nothing but workers. A nest that set itself up under your patio two summers ago is alive and foraging and nowhere near swarming.

If your neighbour has the older colony, that is the whole of it, and it sorts itself out in a year or two without any involvement from you.

Worth ruling out before you conclude anything. A flight runs for a few hours rather than a day, and a modest one from a modest nest is not much of a spectacle. If it went at four on a Thursday while you were at work, there is very little left by the time you get home. The males are dead, the queens have landed and walked off, and what remains is a scatter of shed wings on the paving that mostly looks like grit.

Have a look along the foot of a sunny wall, and the edges of paths. Discarded wings are small and glassy and they blow away fast, but they are the tell.

"Ants" is not one thing, either.

Across most of temperate Europe the black garden ant, Lasius niger, accounts for the bulk of what gets called a flying ant day, and it will take any warm, humid, still afternoon it can get across a long stretch of summer. The yellow meadow ant, Lasius flavus, is the other common one. It lives in lawns and old grassland and probably outnumbers the black ants under a decent garden, and it tends to go up in the second half of August, in flights that are quieter and very easy to walk straight past.

In North America the cast changes but the pattern does not. The cornfield ant, Lasius neoniger, is a standard lawn ant across much of the continent, the black carpenter ant, Camponotus pennsylvanicus, works timber and woodland over much of the east, and in the south the imported fire ant runs a calendar of its own. Elsewhere again the names change and the months move with them.

What does not change is that two species under the same lawn can be months apart, so a garden that is more grass than paving may simply be on a different schedule from the terrace next door.

Mostly it means being clear about which question is on the table.

Whether conditions in your area suit a flight is a tractable problem. Temperature, humidity, wind and recent rain can all be measured and scored. Whether one particular colony under one particular slab goes up on Thursday is not tractable at all, because nobody knows how deep that nest is, how shaded it is, or how old.

Dealate scores the first one for your location from live weather, species by species, and shows the reasoning behind the score rather than asking you to take it on faith. That gets you the afternoons worth walking outside for. Whether your own lawn joins in is between you and the ants. A reason to look up. Not a guarantee.

If you want the wider picture, the 2026 recap covers how badly a single date fits this year, and what is a nuptial flight covers the event itself end to end.