Why Do Black Ants Swarm in One Spot?

Where there is one ant, there is usually another one, or several, nearby. Ants are social insects. They live in colonies where each member performs a job, such as food collection, cleaning or tending to the young. This division of labor contributes to the smooth operation of the nest. They are frequently found in groups around food sources or nesting sites. The food or nest may not visible to humans as it can be covered with several hundred insects at once.

Ants belong to the same insect order as bees and wasps, called Hymenoptera. They are further grouped into the family Formicidae. Ants have a waist-like form at the last thoracic (middle) segment and a bump on their first abdominal segment. The queens and males usually have wings, while the worker ants are wingless. Ants have elbowed antennae, which easily distinguishes them from similar insects.

As social insects, ants need to communicate with each other. They do this by releasing pheromones -- chemical emissions that stimulate a specific response in individuals sensing the pheromone. A pheromone might indicate the site of a food source, or a suitable egg-laying or shelter site. Aggregation pheromones are common in ants. This pheromone causes insects to crowd around a particular area. A large group of ants in one location is an indication that an aggregation pheromone has been released, although the reason for its release may not be evident to humans.

Ants live in many different habitats. They can nest underground, in natural cavities of trees and rocks, in decaying wood, or in non-natural structures. They are a common site near the crevices of sidewalks and between paving stones. Those ants live in the sandy substrate under concrete and bricks, where their colonies can range in size from a few individuals to several thousand.

Large groups of congregating ants can be troublesome. Most ants can bite and some are capable of stinging. A large group of ants crowded around one location is easily removed. Spraying water from a hose will quickly disperse the group. They may return if there is an attractant, such as a food spill or an entrance to an underground nest, at that particular spot. Removing the attractant will prevent the return of the insects. If they persist, insecticides specifically for ants are readily available at home and hardware retailers.