How does a butterfly or moth use its proboscis to drink nectar?

Butterflies and moths (Lepidoptera) possess a specialized, tubular mouthpart known as a proboscis, or haustellum, which is specifically adapted for sucking liquids like nectar.12

This structure is formed by the elongation of parts of the first maxillae, which join together to create a tube. When the insect is at rest, the proboscis remains coiled; however, it is extended when the insect is ready to feed. Once extended, the butterfly or moth uses this tube to draw up nectar from flowers.12

While many adult Lepidoptera rely on this mechanism for sustenance, it is important to note that not all species have fully functional mouthparts. In some families, the proboscis is reduced or vestigial, meaning those adults cannot feed and must rely on energy reserves accumulated during their larval stage.1