ants swarming on the surface of a concrete driveway

Every spring through summer season, I see these ants emerge from beneath my driveway and form these thick swarms on the surface. They typically do this once or twice per day, and after a few hours they go back underground.

After they are gone, there are often some dead ants laying around.

What is the best explanation for this behavior? Why do the ants come to the surface as a group and then seem to later disappear underground?

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    $\begingroup$ type of ants and or a location had been helpful. $\endgroup$ Jun 9, 2023 at 4:48

1 Answer 1


Some hypotheses:

  1. depending of the species, this could be because ants from another colony attack this colony from outside, then many ants inside go out to defend their colony. This could be coherent with the fact that you see dead ones after they quit the surface. This can be supported if you see some of them which are fighting and if you see a line of ants coming from another place.

  2. They are disturbed and think they are attacked, e.g. if you see this everyt ime after you can pass on it, or after you play basketball here, etc. Just try and check if they respond to it.

  3. They are disturbed because of environmental reasons, e.g. after watering your garden, water could suddenly flood their nest.

Less likely:

  1. They just choose the best time of the day (temperature, ...) to clean their nest, including dead ants, but they look too numerous for this.

  2. They may prepare the nuptial flights of the winged ants and group to protect them, but I can't see any on the photo, so probably not.


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