Butterfly ‧ Feeding Habits

What do butterflies feed on? Even primary school pupils know the answer “nectar”. But the true answer is that nectar is not the only food for butterflies. To know what they like, we must first learn about the structure of the mouthparts. The adult butterfly has straw-like mouthparts, so can only feed on fluids.

Caterpillars and adult butterflies have different mouthparts. Caterpillars mainly feed on plants. Mandarin (Citrus reticulata), White Jade Orchid Tree (Michelia x alba), Dwarf Date Palm (Phoenix roebelenii) and Ramie (Boehmeria nivea) are common larval foodplants. Some Blues even feed on small insects like the aphids.

The adults tap nectar from flowers. Lantana (Lantana camara), Billygoat-weed (Ageratum conyzoides), Bidens alba and Chinese Ixora (Ixora chinensis) are important nectar sources. Some adult butterflies love tree sap, rotten fruit, animal excretions and even corpse fluid.

Mouthpart of caterpillars for leave chewing

Mouthpart of adult butterflies for nectar taping

Nectar
Nectar is rich in sugar and is a favourite of butterflies. Flowering plants such as Lantana, Billygoat-weed, Bidens alba, and Ixora are the most popular food sources. Among these, Lantana — a very common plant in Hong Kong — has the highest sugar level. This abundant nectar source best fits the needs of Swallowtails, which are physically large and have large appetites. Some trees also attract butterflies when in bloom. Ivy Tree, for example, is one of the few flowering plants in winter, and attracts many butterflies when it blooms.

Fruits
Many butterflies also like sweet and juicy fruits such as citrus, mango and lychee. Of course, the butterflies cannot peel the skin with their feet! They can only wait for the fruits to become rotten and sip the juices. These rotting fruits are favoured by Nymphs, Browns and Duffers.

Tree sap
Tree sap containing sugar is also food for butterflies. However, butterflies can only eat tree sap after other insects bite through the bark. Nymphs and Browns love tree sap. They are often seen feeding on tree sap in a group, as if they are having a party. Constable craves tree sap. And it is only when it feeds on tree sap that we can closely observe it whilst perched.

Some tree sap is widely popular. Pomelo tree is an example. If you stay beside a pomelo tree, you will have a chance of watching numerous butterflies. Hence many butterfly watchers call it a “Fairy Tree”

Feces
The most surprising food choice for the beautiful creatures is animal faeces! When hiking in the countryside, we avoid stepping on animal faeces. But some butterfly species, the Nymphs, have a special taste for them. In fact, animal and bird faeces retain some nutrients, which can fulfil the butterflies’ needs.

Do butterflies need water?
Apart from food, butterflies need water too. Water contains numerous minerals that are important to butterflies. During the summer, taking in water also helps butterflies to lower their body temperature. They like to sip water on the wet ground or soil. After heavy rain, we can often find a large group of butterflies drinking water from the wet ground. The scene is spectacular, with the party quiet and absorbed in drinking. Swallowtails, Blues, and Whites & Yellows have such habit of drinking in a group.