Flying Ant Day in the Netherlands & Belgium: An Analysis of the 2023-2025 Antscout Data

What is a Nuptial Flight?

The nuptial flight, is the mating ritual for many ant species. During this event, new virgin queens (gynes) and male ants (drones) grow wings and leave their nests in massive, synchronized swarms. They mate mid-air, after which the males die, and the newly fertilized queens land, shed their wings, and attempt to start a new colony.

This synchronization is essential. By flying all at once, ants from different colonies can interbreed, ensuring genetic diversity. This mass emergence is triggered by very specific environmental conditions.

Analyzing Lasius flight hours

The chart shows Lasius flavus (blue), Lasius niger (red), Lasius fuliginosus (green) and Lasius umbratus (yellow). The amount of flights were normalized so that the Y-axis shows the percentage of reports. The current dataset has a size of around ~1000 flights spread over about 3 years.

Lasius fuliginosus confused me, it flies evenly distrubuted over the day, which is the opposite to Lasius umbratus, which pretty much always flies later in the day. It also, though, sees a spike right after the Lasius niger hours.

This chart confirms previous suspicion, Lasius umbratus and Lasius flavus fly after the hours that Lasius niger have nuptial flights. This data doesnt yet show us if they fly on the same day directly after the other species flies. To see this I need to create a different chart.

Lasius umbratus most likely flies after Lasius niger, because the ants would be too busy with the nuptial flight, so that infiltrating the nest would be easier, as Lasius umbratus is a parasitic species. As to why Lasius flavus does this is unclear.

 

Coorolation between Lasius niger and Lasius umbratus flights

This chart shows when Lasius niger, Lasius umbratus flew, or when they had nuptial flight on the same day.

The other 13 flights which were not on the same day as Lasius niger were most likely user error, as not everyone searched earlier in the day.

 

Coorolation between Lasius flavus and Lasius niger flights

The corrolation between flavus and niger is even more distinct, flavus pretty much only flies when niger has flights. Best time to search for Lasius flavus, is after Lasius niger flights around 4 to 6 PM.

 

Coorolation between Lasius flavus and Lasius umbratus flights

This one is a bit more confusing. But flavus and umbratus have pretty much no coorolation. This also suggests that there are different weather conditions needed for both species.

Analyzing other species flight hours

The rest of the species are in way lower quantaties, this data is from around ~500 flights. It still shows some interesting patterns though. Its species Formica rufa (blue), Formica fusca (red), Tetramorium (green) and Myrmica (yellow).

First thing I noticed was how Tetramorium, which is pretty much always caespitum, is found very evenly throughout the day. No big spike in the middle of the day, even though it is data from over 100 flights.

Also, Myrmica seems to fly a bit later than other species, flying from 12 to 7PM.

In this case, the host species Formica fusca flies later than the parasitic Formica rufa. These species mostly do not really fly on the same months, and the dataset is too still small to make conclusions. Especially Formica fusca is not found very often.

Analyzing weather conditions

Maximum Temperature

This chart shows the amount of flights relative to temperature, some species are found more often than others, so just look at the distrubition of the species instead of the height of the lines. The only two things i’ve noticed actually matter are temperature and wind speed, especially wind gusts. Besides that, uv-index and surface pressure may play a role too.

 

Maximum Wind Gusts

This chart shows the amount of flights relative to wind gusts.

Looking at these two charts it may look like weather conditions for nuptial flights are the same for all four species, but this is most likely not the case, as they mostly do not fly on the exact same days. This suggests a piece of the puzzle I am missing. There most likely is not any magical variable that precisely indicates whether they fly or not though.

 

Relative Humidity

The chart with amount of flights relative to humidity is a bit more complex. The dotted line is the average humidity over both the flights, and days without flights. So this would look like the flights occured on days where the humidity is low. But this is not the case, because the chart includes days with rain which bring the mean humidity higher.

 

Relative Humidity without days with rain

Thats better, without the days where there was rain, the dotted line, which is the average humidity, is now lower than the peak flight spike. Which means, ants have a higher chance of flying if theres higher humidity. This isn’t an actual hard limit though, so it is hard to use it for predictions. Not impossible though! especially when used allongside other variables.

 

Surface pressure flight day, 1 day before and 2 days before

It’s a key factor in determining weather patterns, with high pressure generally associated with settled, clear weather and low pressure often linked to unsettled, stormy conditions. It has a pretty big coorolation, even though it does not look like it, paired with other variables this is a very strong indicator of when flights happen.

The mean line is lower than the spike of flights, which means the surface pressure is higher when flights occure, even though they also appear below and above the average line, its way more often above.

This coorolation seems to be for the day of the flight and the day before, then being average again for the third day. This might indicate a pattern of there needing to be two days of high surface pressure for a flight to occure. This is interesting, I noticed that the prediction model I made for Netherlands and Belgium was way more accurate and could way more easily find patterns when I added all three days of surface pressure. With only the flight day, it would not be nearly as accurate as with all two or three days.