Aphids are very small insects that feed on plant sap.
They measure about 1 to 10 millimeters, can be different colors from green to black, and have mouthparts that pierce the plant and suck its sap. Some have wings, but most do not and do not move much on the plant.
They reproduce extremely quickly and attack all kinds of plants, from vegetable crops to ornamental plants.
They feed on the softer parts, such as young leaves and shoots, and by sucking sap they produce honeydew, a sugary substance that can lead to a fungal disease called sooty mold, but it also attracts other insects such as ants, which feed on it.
There is in fact a very particular relationship between aphids and ants: ants protect aphids and carry them from one plant to another to make sure they keep producing honeydew.
In addition, through their saliva they can transmit viral diseases from one plant to another, risking serious damage.