The word 'feeler' often relates to parts of small animals or insects, rarely used for larger animals. The caterpillar has tiny feelers on its head.
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Sensing Role
'Feeler' usually refers to body parts that deal with touch or environmental sensing, not taste or sight. Crabs have feelers to examine objects in their path.
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Literal Use
Use 'feeler' in a literal sense only when describing a physical part of an organism. The snail's feelers retracted when touched.