Butterflies Taste With Their Feet

On a warm evening, a large butterfly settles on a leafy window box above a cobbled street and seems to do nothing at all. A squirrel hurries past below, a badger ambles by on its evening round, and the butterfly simply stands on a leaf. It looks like resting. In fact it may well be tasting, and it is doing it with its feet.

This is not a figure of speech. On the website of Carleton University’s biology department, the biologist Jayne Yack explains that many insects, including butterflies, have contact chemoreceptors on their legs. Her colleague Naomi Cappuccino describes these receptors on the feet, known as tarsi, as working in a similar way to human taste buds. Butterflies also taste through their proboscis, the long mouthpart they drink with, and pick up airborne chemicals with their antennae.

The feet matter most to females, because they face the biggest decision in a butterfly’s life: where to lay eggs. As Cappuccino puts it, a female’s main concern is finding an appropriate plant for her offspring to feed on. So she lands on a leaf and, as the university’s greenhouse manager explains, drums it with her feet to release the plant juices, searching for the right plant chemicals. If the chemistry is wrong, she moves on.

Laboratory work shows how detailed this can be. A 2026 study in the Journal of Chemical Ecology, by Nishioka, Sasaki and Ozaki, looked at a swallowtail butterfly called Papilio xuthus. It describes how egg-laying females assess leaf chemistry by drumming the leaf surface with taste organs on the underside of their front feet, and how each of these tiny sensory structures houses up to four taste neurons. The females detect plant compounds that do not evaporate, through direct contact with the leaf.

The same study shows that the feet are also used to say no. This butterfly’s host plants belong to the citrus family, Rutaceae. When the researchers tested extracts from five plants belonging to other families, egg-laying was completely suppressed. In other words, the female is not only searching for the right leaf. Her feet are actively detecting the wrong ones and turning them down. It is a quiet, step-by-step inspection that nobody watching from the street would ever suspect.

How do we know? By recording the signals from these sensory structures and by watching what females do on real leaves and on plant extracts. Whether butterflies experience flavour the way we do is another matter. As Carleton’s Jeff Dawson puts it, it is very unlikely that humans and butterflies perceive the deliciousness of an orange slice in the same way. But the butterfly on the window box may well be learning something about the leaf beneath its feet, one careful step at a time.