How can butterflies and moths smell?

How can butterflies and moth find food-plants and mates by smell if they don't have a nose? Ecologist Alex Morss explains how they can sense with other parts of their body.

Common blue butterfly in Weymouth, Dorset, UK. © Verity Hill

Butterflies and moths lack a ‘nose’, yet they rely heavily on smell to find mates and food-plants, and in order to detect fungal diseases and parasites.

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Each butterfly or moth has thousands of finely tuned smell and taste receptor scales, bristles and pits. These are located on its feet, on its palps (moustache- like mouthparts) and on its antennae. The insects can thus distinguish countless plant and insect chemicals that waft on the wind in a complex, ever-changing gaseous ‘soup’.

A male emperor moth can locate a female 8km away at night, by smelling her pheromones. Monarch butterflies search for milkweed, which their caterpillars eat, by combining visual cues of shape and colour with scent.

Swallowtail butterflies use their antennae to pick up the aroma of their caterpillar food-plant (usually milk parsley in Britain), then before laying any eggs they drum their feet on it to confirm the scent and taste.


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Main image: Common blue butterfly in Weymouth, Dorset, UK. © Verity Hill