Why we won't tell you when tropical ants fly

For locations within 23.5 degrees of the equator, Dealate's species list withholds generic flight-month estimates. Those estimates would need local evidence to be useful.

Temperature, rainfall and daylight can all vary through the year, but their patterns differ between climates. A British Lasius niger flight calendar cannot establish when a tropical species will fly. Even a rain-triggered flight can be seasonal where rainfall has a regular wet season.

The best-documented case is a leafcutter ant, Atta vollenweideri, studied over 23 swarm events in northern Argentina. Flights only happened once cumulative rainfall over the preceding month reached at least 64 mm, about 2.5 inches. Even then, alates stayed in the mound until air temperature on the days following rain rose above 26 °C, 79 °F, with the actual takeoff clustering closer to 32 °C, about 90 °F. In those observations, rain and temperature both mattered.

That's one well-studied genus in one region. It's a real result, and it's also exactly the kind of finding that shouldn't be generalised past its own species. Extrapolating an Argentine leafcutter's rain threshold onto, say, a Malaysian Oecophylla colony would be inventing a fact, not reporting one.

Moving a northern temperate calendar six months forward cannot establish a tropical flight season. Local rainfall records and dated observations of winged ants are more useful evidence.

Dealate's location pages and forecast treat this separately. Location pages withhold generic month windows within 23.5 degrees of the equator. The forecast uses a season-neutral fallback there, with dedicated rules for some researched genera. That fallback describes a limit in the forecast's evidence; it does not mean tropical ants have no seasons.

The guide to flights below the equator explains regional estimates and their limits. Why the forecast and your garden disagree covers the smaller differences a weather forecast cannot resolve between nearby gardens.

The Atta vollenweideri rainfall and temperature thresholds are from Staab, M. & Kleineidam, C.J. (2014), Initiation of swarming behavior and synchronization of mating flights in the leaf-cutting ant Atta vollenweideri, Myrmecological News 19: 93 to 102, 23 swarm events recorded in northern Argentina between 2004 and 2010. The full source list behind the forecast model is set out on the methodology page.