Ants and aphids have a symbiotic relationship. In this kind of relationship, two different types of animals benefit one another. Aphids provide food for ants, while the ants protect the aphids from predators.
Black bean aphids being milked by ants
Aphids primarily eat sugary sap, which they suck from host plants. Being hungry little fellows, aphids drink a ton of sap and excrete a ton of waste. This waste is called “honeydew” and is a tasty, nutritious meal for ants.
Aphids are considered pests because they will feed on a plant’s nutrients, causing it to wither. However, they are an essential food source for ants.
The sugar-rich excretion is so tasty that ants will “milk” the aphids to obtain it. To do this, ants stroke aphids with their antennae, causing honeydew to be released. Some aphid species must rely on milking to excrete honeydew at all. Therefore, they are very dependent on ants, since they require them to excrete waste.
Ants take care of aphids like a farmer would take care of a herd of cows. When the host plant that the aphids are feeding on is depleted of all nutrients, the ants will carry their aphids to another plant. The ants also defend the aphids from other insects and parasites. Ants even destroy the eggs of known aphid predators, such as ladybugs. Some ant species will help aphids survive the winter as well. They carry the aphid eggs into their anthills to protect them from the cold. They are sure to store the precious eggs where temperatures and humidity are optimal. They are so meticulous that they will move the eggs if the surrounding conditions change! In spring, the aphids hatch, and the ants will carry them to a host plant so they can feed.
The ladybug larvae is a predator of the aphid
Aphids, unfortunately, trade their freedom for a safe life with the ants. Aphids are almost always wingless. If the aphid population becomes to large or food sources start to deplete, aphids will grow wings and fly to a new location to search for food. Ants have been seen tearing the wings from aphids to prevent the loss of their food source. Semiochemicals (chemical substances or mixtures that carry a message meant for communication purposes) produced by ants can stop aphids from developing wings.