What Do Butterflies Eat? Nectar, Fruit, Sap and Mud

How butterflies drink: the proboscis

A butterfly has no jaws for chewing. Instead, its mouthparts form a long tube, the proboscis, that stays coiled like a watch spring under the head when not in use. To feed, the butterfly uncoils it and pushes the tip into a flower or onto a wet surface.

The proboscis is made of two halves zipped together along their length. Studies of its structure suggest that it works partly like a sponge or paper towel, drawing liquid into tiny grooves near the tip, and partly like a drinking straw, with muscles in the head pumping the liquid up to the gut. This lets butterflies drink from both deep flowers and thin films of liquid on a fruit or stone.

Proboscis length matches diet. Butterflies that visit long, tube-shaped flowers often have long tongues, while fruit-feeders tend to have shorter, sturdier ones.

Nectar: the main food of most butterflies

For most butterflies, flower nectar is the main fuel. Nectar is sugar water with small amounts of amino acids and other nutrients. The sugars power flight, which is why butterflies are most active on warm, sunny days, when they can visit dozens of flowers in a row.

Butterflies prefer flowers that offer a landing platform and easy access to nectar. Clustered flowers such as asters, thistles, knapweeds, clover, buddleia, lavender and milkweed are favorites in Europe and North America. The painted lady, for example, drinks from a wide range of meadow and garden flowers, refueling constantly during its long migrations.

Butterflies find flowers by sight and smell. They see colors, including ultraviolet patterns invisible to people, and they smell with their antennae. They can also taste with their feet, as explained in do butterflies taste with their feet?

Rotting fruit, tree sap and honeydew

Many butterflies, especially in forests, rarely visit flowers. In Europe and North America, the red admiral, comma and mourning cloak often feed on fermenting fruit such as fallen apples, plums and pears. Tree sap oozing from wounds in oak or birch trunks is another favorite, and the purple emperor of European woodlands famously feeds on sap, dung and even carrion.

Honeydew, the sweet liquid produced by aphids and other sap-sucking insects, is a useful food source in trees where flowers are scarce. In the tropics, many large butterflies such as morphos and Charaxes species feed mainly on rotting fruit.

Mud, salt and minerals: puddling

Groups of butterflies are often seen sitting on damp sand, mud, or animal droppings. This is called puddling. Nectar is low in salts, so butterflies use these wet surfaces to take in sodium and other minerals.

Puddling butterflies are mostly males. When a male mates, he passes a package of sperm and nutrients to the female, and this nuptial gift includes sodium that helps her produce eggs. Some tropical butterflies even drink the sweat of people or the tears of turtles and caimans for the salt they contain.

Pollen-eating butterflies

A few tropical butterflies of the genus Heliconius, found from the southern US to South America, collect pollen on their proboscis. They release saliva onto the pollen, which dissolves its proteins, and then drink the result. This protein-rich diet is linked to their long adult lives, which can last several months, far longer than most butterflies.

What do caterpillars eat?

Caterpillars are eating machines. They have strong jaws for chewing leaves, and their job is to grow as fast as possible before turning into a chrysalis. Most species eat only one plant or a small group of related plants, called host plants. The female butterfly lays her eggs on these plants so the caterpillars hatch on their food.

A few caterpillars are carnivores. The harvester (Feniseca tarquinius) of eastern North America has caterpillars that eat woolly aphids. In Europe, the large blue (Phengaris arion) starts on wild thyme, then tricks red ants into carrying it into their nest, where it eats ant grubs.

How a leaf-chewing caterpillar becomes a nectar-sipping butterfly is explained in how does a caterpillar turn into a butterfly?

Do some butterflies not eat at all?

Nearly all adult butterflies feed. Some moths, such as the luna moth and many silk moths, have no working mouthparts as adults and live only on the fat they stored as caterpillars. Among butterflies, adults that cannot feed are extremely rare.

Myths and facts

Myth: Butterflies eat pollen like bees. Fact: Most butterflies only drink. They may carry pollen between flowers, but only a few tropical Heliconius species feed on it.

Myth: Caterpillars eat any plant. Fact: Most caterpillars are picky and starve if their host plant is missing, which is why protecting wild host plants matters for butterfly conservation.