clicking by caterpillars

Definition

An acoustic defensive behavior in which caterpillars produce audible clicks or snaps by forcefully retracting the head and thorax, causing mandibles or specialized cuticular structures to strike the substrate or each other. The sound serves as an aposematic signal to predators or as a startle response, often preceding or accompanying regurgitation of defensive secretions. Documented primarily in Bombycoidea (especially Sphingidae and Saturniidae), the behavior is considered a form of deimatic display.

Etymology

From Middle English 'clicken' (to make a sharp sound) + 'caterpillar' (larval stage of Lepidoptera).

Example

When disturbed, late-instar walnut sphinx caterpillars (Amorpha juglandis) arch backward and snap their mandibles against the leaf, producing a series of sharp clicks that coincide with the release of distasteful oral secretions.

Synonyms

• mandible clicking
• defensive clicking

Related Terms

• stridulation
• deimatic behavior
• startle response
• aposematism
• regurgitation defense
• acoustic aposematism
• Bombycoidea

Usage Notes

Distinguished from stridulation, which involves rubbing specialized body parts together; caterpillar clicking relies on percussive mandible strikes. Not all clicking caterpillars are aposematic—some species use the sound in intraspecific communication. The behavior is most thoroughly studied in sphingid caterpillars, where it correlates with the presence of defensive glands.