Flying ants.

At work, we have a small wall where passengers can sit and wait. In this wall there are at least five different ant colonies. Today seemed to be the day that the flying ants left the nest, which isn’t surprising seeing as it was both a warm and dry day (which has been rare over the last month).

Due to the nature of my job I got to spend a lot of time around the wall, and noticed, without exception, that all the flying ants were taking off in the same direction, which I calculated to be roughly an easterly direction. Now, today was a very still day, with very little wind, so I discounted the idea that the ants were being blown in that direction. In fact, when an obstacle (such as my co worker) was placed in their flight path, the ants dodged him and then readjusted their course to make it an easterly one. I also discounted the fact that they were somehow being influenced by the sun. I observed this behaviour over a few hours, and the course that they took never changed.

Why do they all head in the same direction, and how do they calculate this direction?

There was also some controversy over what flying ants are actually for. What do they do? Do they move out to form even more colonies for next year (in which case the fact that they all fly in the same direction is even more perplexing, surely it would be better to fan out?) or do they perform some other function?

In the first place the last time I saw a bunch of flying ants moving out in the same direction; they turned out to be termites. It is at least worth checking out. What has happened is that perspective queens have also left the nest (they are a few of the flying insects). The majority are horny males that are hunting for the females. There probably isn’t an explaination of how they know the right direction but it obviously helps the process. I have no idea what happens to all the males, except they lose their wings after the chase is over. :frowning:

Termites in the UK? These are definitely ants, the small “worker” ants were crawling everywhere.

I have never noticed any specific orientation in an ant nuptial flight swarm before but, since they are strongly attracted to ultraviolet light, possibly they are heading towards the strongest source of UV light. Since most ant swarms occur on warm, sunlit days this means that the dispersal is random as the UV light from the sun is distributed everywhere. In your case, they may be orienting towards a reflected light source - like a white building wall maybe?
As for what the flight is for, it is an instinctual mating flight of queens with attendant males heading out to start new colonies.

There are a few localities in the UK where termites have been inadvertently introduced and are somewhat naturalised, but the next ice age will kill them off.

Flying ants seem to co-ordinate their nuptial flights by the weather; humid, thundery afternoons in late summer are favourite. I don’t know how they orient themselves, but it probablky is just by the direction of the sun; if you know the position of the sun and the time of day, you can calculate a fixed direction (although the ants won’t be doing the calculation consciously, of course).

Their cousins, bees, can work out the direction of the sun even on a cloudy day by sensing the way in which daylight is polarised.

There’s no buildings nearby. The wall is part of a platform, really just a strip of tarmac, for a miniature railway, in the middle of the woods.

As I said, the ants took off over a period of several hours, which is why I discounted the sun. I wasn’t the first to notice the direction that they were all flying, my co worker was.

How high are the chances of survival for an individual flying ant? There appeared to be thousands of them flying off, but I doubt that many new colonies will be created. I noticed birds pecking at the swarming mass, so roughly how many new colonies will be created?

Since the population of ants is fairly stable, on average (across all nests and across a good deal of time, probably) only one new queen from each nest survives; if it was more than an average of one, the population would be on the increase constantly.