Many ants can see in the dark – some ants forage in the night and have more sophisticated night vision compared to daylight ants.
Ants have compound eyes with which they can visually perceive their surroundings. However, their resolution is very low compared to humans, and as a result, their vision is very blurry. Some ants see better than others depending on their body sizes, where bigger ants generally see better than smaller ones.
However, there are ants such as army ants and driver ants that are completely blind and rely on other methods to find their way around.
What Makes Up Ants’ Eyes?
Ants’ compound eyes have numerous units known as ommatidia or facets. These units make the eyes look like an array of LEDs found in traffic lights, albeit dome-shaped.
Every single ommatidium sees one point of an object such that the whole eye will see one image but different parts of it.
As aforementioned, the resolution of ants is way lower than that of humans. One way to determine the approximate resolution of ants is by counting the number and measuring the diameter of the ommatidia.
This can be achieved by spreading a layer of transparent nail polish over the eye of a dead ant, letting it dry, then peeling it off. The nail polish comes off with a replica of the ant’s eye. The parameters can then be obtained, and the ant’s spatial acuity calculated.
How Do Ants See in The Dark?
Ants usually live in dark places like tunnels, wood, or underground. Ant species like carpenter ants, sugar ants, and bull ants forage at night when it is absolutely dark. Yet, they are able to find their way in these dark places, raising the question as to how they see in the dark.
First of all, it is important to acknowledge that ants have a special system of communication where they use a hormone called pheromone to send signals to each other.
They also use their antennae to feel their way around, especially for the blind ants. More importantly, ants have special eye adaptations to enable them to see in the dark.
Generally, ants that are adapted to seeing in darker placer have a larger eye anatomy than other ants. They have a bigger eye area, facet size, eye lenses, and ocelli size compared to day-active ants.
For instance, carpenter ants and sugar ants, known to forage at night, have eyes filled with wide photoreceptors (or rhabdoms), making for a remarkable night vision. The concept of photoreception will be discussed better later in the article.
Color Perception at Night
According to experts, ants have three photoreceptors with which they can perceive colors: UV, blue and green. Photoreceptors are cells in the eyes that are sensitive to light. Considering that most mammals (including humans) have only two photoreceptors, ants have a very good perception of colors.
Bull ants, in particular, can perceive UV lights, while humans can’t. This means that they can see more colors than humans. What’s more, ants can perceive these colors very clearly at night, even at light levels where humans are completely color blind.
Nocturnal ants rely heavily on their sophistication of color vision to navigate around. This adaptation is due to the fact that, unlike other ants, these nocturnal ants forage individually. Therefore, they cannot rely on pheromones as they don’t have partners to communicate with.
Additionally, ants’ low visionary resolution makes it difficult to identify landmarks, especially at night. Therefore, having accurate color vision is really helpful in recognizing landmarks and finding their way back to their nests.
How Far Can Ants See at Night?
It is difficult to determine just how far ants can see because there is no way to measure that. The compound-eye structure makes this impossible. Unlike humans and several other mammals, ants do not have a focal distance as they lack a lens and a retina. This is due to the nature of their compound eyes.
The reason human beings can tell how far they can see is that they have a focal point, which differs from one person to the next.
Ants, therefore, presumably form images in much the same way as a digital camera with low pixel resolution, where each facet of the compound eye corresponds to one pixel. In other words, distance from an ant’s eye is irrelevant because all images are blurred anyway.
However, bigger ants are said to spot obstacles from a further distance compared to smaller ants. This follows the concept of miniaturization, where the smaller an insect is, the slower and less quality are its body functions. Thus, the smaller an ant, the blurrier its vision- meaning they have less spatial acuity.
An observation was made by scholars to determine how far different ant sizes begin to notice and react towards obstacles. Two types of ants, the Australia Bull ants, which range from 8mm to 45mm in size, and electric ants, which are 1.5 mm big, were put to the test.
The scholars observed that the bull ants would detour from 17cm away, while the smaller electric ants would start detouring from a distance of 5cm away from the obstacle.
Most ants can see, although their vision is not as good as that of humans. They have a very low relative resolution, and all the images they perceive are super blurry. However, they have excellent photoreceptors with which they can perceive three different colors; blue, green, and UV.
Many ants can also see in the dark and have eye structures that are adapted to night vision. But others like driver ants are blind and can’t see at all.