Why butterflies taste with their feet
Butterfly feet carry contact chemosensilla: tiny porous hairs whose receptor neurons respond when dissolved molecules touch them. For females, that first taste can determine whether a leaf is a suitable nursery for caterpillars.
Scope: Contact chemoreception on butterfly tarsi, especially female host-plant assessment, while distinguishing foot receptors from the broader taste system on antennae, mouthparts, and ovipositors. · Last updated
Put receptors at first contact
Legs often touch a leaf or flower before the proboscis does, making tarsal receptors a fast checkpoint. Each contact sensillum is a hair-like cuticular structure connected to sensory neurons, with an opening that admits nonvolatile compounds in surface moisture. Different neurons can respond to sugars, salts, amino acids, bitter deterrents, or more specialized plant cues and send distinct firing patterns to the nervous system. [1][4]
Drum a leaf to release chemicals
An egg-laying female may repeatedly tap, scrape, or drum a leaf with her forelegs. The action increases contact with surface compounds and can expose chemicals from plant tissue. Monarchs touch potential milkweeds with forelegs, middle legs, and antennae, while checkerspots pause and taste multiple parts of a candidate plant. Behavior varies, but landing begins an active sensory inspection rather than a passive footstep. [2][3]
Recognize a chemical combination
A host is rarely identified by one universal flavor. In studied swallowtails, sex-specific foreleg sensilla contain receptor neurons tuned to several oviposition stimulants, and a particular mixture evokes stronger egg-laying behavior than its components alone. This helps a specialist distinguish a plant that its caterpillars can eat from a chemically similar neighbor, while visual shape, color, texture, odor, and plant condition also affect the decision. [1][4]
Taste with more than the feet
The phrase 'taste with their feet' is memorable but incomplete. Monarch experiments found relevant contact receptors on several legs and antennae, and adult Lepidoptera may also carry gustatory sensilla on the proboscis, mouthparts, or ovipositor. Males and females can differ sharply in foreleg anatomy because females must evaluate larval food. Species that use different host plants likewise evolve different receptor complements and behavioral tests. [1][2][3][4]
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Where this guide comes from
Source-checked editorial guide. Last updated . This guide teaches identification and field skills; it is not a substitute for expert verification when it matters.
- Communicative & integrative biology — An oviposition stimulant binding protein in a butterfly: Immunohistochemical localization and electrophysiological responses to plant compounds ↗
- Physiological Entomology — Contact Chemoreception in the Monarch Butterfly ↗
- Journal of chemical ecology — Oviposition cues for a specialist butterfly--plant chemistry and size ↗
- The Journal of neuroscience : the official journal of the Society for Neuroscience — Gustatory sensing mechanism coding for multiple oviposition stimulants in the swallowtail butterfly, Papilio xuthus ↗
