Australian painted lady in the context of "Septal nectary"

Nectar is a viscous, sugar-rich liquid produced by plants in glands called nectaries, either within the flowers with which it attracts pollinating animals, or by extrafloral nectaries, which provide a nutrient source to animal mutualists, which in turn provide herbivore protection. Common nectar-consuming pollinators include mosquitoes, hoverflies, wasps, bees, butterflies and moths, hummingbirds, honeyeaters and bats. Nectar is an economically important substance as it is the sugar source for honey.

Nectar is also useful in agriculture and horticulture because the adult stages of some predatory insects feed on nectar. For example, a number of predacious or parasitoid wasps (e.g., the social wasp species Apoica flavissima) rely on nectar as a primary food source. In turn, these wasps then hunt agricultural pest insects as food for their young.

In zoology, a nectarivore is an animal which derives its energy and nutrient requirements from a diet consisting mainly or exclusively of the sugar-rich nectar produced by flowering plants.

Nectar as a food source presents a number of benefits as well as challenges. It is essentially a solution of (as much as 80%) the simple sugars sucrose, glucose and fructose, which are easily ingested and digested, representing a rich and efficient source of nutrition. This solution is often diluted either by the plant that produces it or by rain falling on a flower and many nectarivores possess adaptations to effectively rid themselves of any excess water ingested this way.