Aphids are small, delicate, millimetre sized insects. Their structure is very diverse and there are frequent differences between the sexes. On the head, they mostly have short filamentous antennae with elongated first segments and small compound eyes. The stinging sucker occurs between the first pair of legs on the thorax. The membranous wings are small, often completely reduced in females. On the upper side of the fifth segment of the back there are two short tubes (sipunculae), through which they secrete sticky substances to defend against predators. They are mostly green or light brown in colour.

This family includes about 5000 species of insects that inhabit all continents, although with greater diversity in temperate climates. Adults feed on plant sap and, at high densities, can cause damage to cultivated and ornamental plants. They are also known as vectors of various plant viruses. They often reproduce asexually with unfertilised eggs. Females can be viviparous and there are known cases when unhatched individuals have developing embryos inside them. This allows aphids to quickly respond to a rich food sources by increasing their population. When the food source dries up, winged individuals usually develop and reproduce sexually. They mostly overwinter in the egg stage. Some species are ant-loving and attract ants with secretions from their digestive tract, which contain a lot of sugars. In exchange for this rich food source, the ants protect them from predators.