Why can’t ants walk on chalk or ink? (Quickly Answered)

In the warm season, ants are particularly active and spread rapidly. They can be seen almost everywhere and populate gardens, terraces, and houses. Usually, they appear in large numbers and their presence can be uncomfortable and annoying.

This need for simple and effective tools keeps videos and tips popping up recommending the use of chalk to keep the ants away. But how exactly does it work and why can’t ants walk on chalk?

Ants communicate via scents (pheromones) and thus indicate the route by which food can be found. This marked road is interrupted by chalk and the ants are irritated and deprived of their orientation. In the case of ink, there are also chemicals that deter the ants. It can also be difficult to walk on the new surface.

But the effect of chalk is limited and only available for a short time, which makes the use less effective. In this article we describe the exact mode of action, explain when you should use chalk and ink and which better home remedies are available.

How do ants orient themselves?

Ants live together in social structures with a defined hierarchy and specific tasks for each caste. The workers do have even more subtasks, such as nest care or the procurement of food.

Scout ants play an important role. Their task is to find food in the area and to inform the state about this new source. In this case, they use scents (pheromones) for the navigation.

Ant trails are created by scents (pheromones)

These pheromones mark their way from the nest to the food source. More ants follow this scent path and the well-known “ant trails” are created.

By repeatedly using this path, more pheromones are exposed and the path becomes more and more distinct and clear for the insects. This can easily result in a large number of ants on the road.

In addition to the use of scents, ants also use tactile signs and the presentation of movement patterns to pass on information. Sensing with their feelers is of particular importance in social interaction.

However, the use of pheromones has the greatest influence on orientation. These enable particularly effective use of the available resources.

Despite this great importance, there are never all ants on such a path and it is neither the only source of food. Such a dependency would put the ant colony at high risk.

Why can’t ants walk on chalk?

Ants that walk onto a chalk line are temporarily held back from their movement pattern and often change direction because the pheromone trail they are following is interrupted. The chalk also changes the structure of the soil, which could be negative for the insects.

Chalk consists of a calcareous material and is enriched with substances that make it more stable and give it its color (if any). If a chalk line is drawn on a surface, the lime molecules combine with the surface.

This contact with the ground interferes with the trail that the ants made. The pheromones are removed at this small point and the path is broken. This creates an unexpected difficulty in orientation.

In addition, the surface is now covered with a fine powder, which can be an alarm signal for the ants. They notice the change in structure and become more cautious.

In addition, depending on the type of chalk, it may contain other components that cover the pheromones. Ants react very sensitively to such scents and change their behavior immediately.

Why can’t ants walk over ink?

If ants encounter a line drawn with a pen, they do not cross it because the ink contains chemicals that interrupt the existing pheromone path and represent an interfering signal.

The ink in a fountain pen or ballpoint pen contains not only color but also other substances that give the ink its properties. With a fresh stroke, these substances evaporate quickly and release the chemicals into the ambient air.

These subtle smells are imperceptible to us humans but represent a striking change for the ants. On the one hand, these smells cover the pheromone path and on the other hand, they are an alarm signal that the insects detect and avoid. These include methylbenzene and xylene.

Ants and chalk: Advantages and Application

Chalk breaks up the existing path and prevents ants from entering or leaving certain areas. Use as an effective control agent should therefore be a good alternative. However, this is only shown to a limited extent in practical application.

After all, chalk’s useful benefit is to create a short-term interruption of the ant trails. If the ants are suddenly on a path into the house, the flow can be temporarily stopped with a line of chalk.

Chalk is short-lived and not effective in the long term.

The effect is limited, however, because the ants quickly get used to the obstacle and reactivate their pheromone trail after a short time. The effect fizzles out and the insects simply run over the chalk line.

Nevertheless, chalk has a decisive advantage over other ant remedies. Chalk is cheap, effective for a short time, and above all not harmful!

Drawing a chalk line does not affect children and pets and can be used anywhere. The ingredients do not harm the environment and the soil and groundwater are not affected.

This makes chalk a good, natural way to gain some time before solving the real problem.

Ants and chalk: Cons

The biggest disadvantage of chalk is its (mentioned) time-limited effectiveness. The effect is no longer given after a few hours. A permanent redrawing of the line would be necessary – but is impractical and ineffective.

In addition, chalk can only be actively used in a certain environment. It is not possible to draw a line on uneven ground. Only firm and even floor coverings such as tiles, stones, and floorboards can be marked.

If the colony is inside the house, an interrupted ant route is not helpful either. The ants will take another route or another source of food. The nest will continue to exist and may cause damage to the house.

A broken path also robs you of a good starting point for long-term and effective ant control. If the nest has to be removed (for example in the house), the queen must be killed.

Ant trails should be used for pest control.

This is done primarily with ant baits that contain an attractant and some poison. The poison is transported into the nest with the food and fed to the offspring and the queen. Ideally, she dies a few days later from this dose.

It is necessary that the bait is picked up by the workers. An ant trail is perfect here! The bait just needs to be placed on this path. As a rule, it is very actively accepted shortly and the effect occurs quickly.

An ant trail should therefore not be blindly destroyed by chalk if it can be used to control insects.

Not all chalk is created equal.

“Anti-ant chalk” (preferably from Asia), which kills the ants that come into contact with it, is advertised on the Internet widely. The effect is true to some extent, but it is due to the insecticides that are in the chalk.

A poor table of contents and difficult dosages make this chalk dangerous for animals and humans!

Alternative to chalk: Diatomaceous earth

The limited range of uses of chalk can be expanded significantly with Diatomaceous earth (kieselguhr) and the disadvantages can be almost eliminated.

This powder consists of finely ground remains of mussels. The powder is microscopically sharp-edged and injures the exoskeleton of the ants, which die within a short period. In most cases, however, they avoid contact.

Diatomaceous earth is non-toxic and has a long-term effect. It can also be used on uneven surfaces. Although it does not remove the nest, it is the most effective barrier.

It is also very inexpensive and easily available on the Internet and all hardware stores.

The only downside to the fine powder is that it shouldn’t be inhaled. With normal handling and distribution in a protected area, however, this no longer plays a major role.


Martin is the head of pestABC.com and he loves to share his research and experience with you.

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