Lasius neoniger and the Labor Day flights

Most American ant flights pass without a name. Lasius neoniger got one. Across the Northeast and Midwest its colonies swarm in the last days of August and the first days of September, reliably enough that people started calling them Labor Day ants, and the nickname stuck because the calendar keeps half-confirming it. Labor Day 2026 falls late, on 7 September, so this year the ants will mostly have gone first.

The species itself is about as ordinary as an ant can be. The cornfield ant nests in open turf: lawns, sidewalk margins, baseball infields, and famously golf courses, where the little soil craters it throws up around nest entrances make greenkeepers grind their teeth. It's the ecological twin of the black garden ant that owns Britain's July, a Lasius of open sunny ground, running the same script five weeks later on another continent.

Here's the genuinely odd thing about neoniger, and it comes from one of the better datasets in this whole field. In 2016, researchers at the University of Oklahoma fitted purple martins with altitude loggers and identified the insects the birds brought back to their chicks, effectively using the martins to sample the sky. Most flying ants in that dataset turned up throughout the lower atmosphere, to about 160 m, roughly 520 feet. Lasius neoniger didn't. Despite having light queens that should ride the air easily, it appeared only below about 22 m, around 72 feet, and the authors note its queens mate on or near the ground rather than in high aerial swarms (Helms et al. 2016).

Which explains something every Northeasterner who's walked through a Labor Day flight already knows in their body. Other species' flights happen mostly overhead, a shimmer against the clouds. This one happens at eye level. The same number of ants, compressed into the bottom 20-odd metres (about 65 feet) of air, reads as a wall rather than a haze. You don't watch a neoniger flight so much as stand inside it.

For a keeper this is excellent news, because everything is happening within reach.

The queens are the big ones: dark brown, heavy-shouldered, obvious against the clouds of much smaller males. Freshly landed queens break their wings off within minutes and start running for cover, so the productive search is the pavement and bare soil right after the swarm thins, not the swarm itself. How to tell a queen from a large worker covers the thorax-and-wing-scar check if you're unsure what you've picked up.

Founding is standard Lasius, which is to say the easy kind: fully claustral. She seals in, feeds nobody including herself, and raises her first workers off her own reserves. Test tube, water, cotton, darkness, patience. Fully claustral or not explains the whole system, and you caught a queen this week, now what is the first-week manual. Don't feed her; she brought lunch.

One more layer, because neoniger's story has a villain. The citronella ant Acanthomyops murphyi founds its colonies as a temporary social parasite: its queen doesn't dig her own nest but gets herself adopted into a Lasius neoniger colony, where her brood is raised by the host's workers until they've replaced them (Cover & Sanwald 1988). If that trick sounds familiar, it's the same one Europe's Lasius umbratus plays on the black garden ant, which we covered in the parasitic Lasius, running in Europe with different players.

The flights want warm, humid, still afternoons, and the day after rain is the classic setup. Beyond that, the precise date wobbles year to year with the weather, latitude and luck, which is exactly the gap a day-by-day forecast exists to fill. Dealate scores neoniger alongside whatever else is in season at your location, hour by hour, so a promising first-of-September afternoon stands out from an empty one. A reason to look up, not a guarantee. Or in this species' case, a reason to look straight ahead.

Helms, J.A., Godfrey, A.P., Ames, T. & Bridge, E.S. (2016). Predator foraging altitudes reveal the structure of aerial insect communities. Scientific Reports 6: 28670. Source of the flight-altitude data and the ground-mating note for L. neoniger.

Cover, S.P. & Sanwald, R. (1988). Colony founding in Acanthomyops murphyi, a temporary social parasite of Lasius neoniger. In Advances in Myrmecology, 405 to 417. Source of the host relationship.