Crochets

Definition

Hook-like, sclerotized spines arranged in rows or circles on the ventral surface of abdominal prolegs in caterpillars (Lepidoptera larvae), used to grip the substrate and aid in locomotion and anchoring. Crochets are diagnostic taxonomic characters; their arrangement (uniordinal, biordinal, triordinal, or multiordinal) and whether they form a complete circle or a mesal penellipse helps distinguish families and subfamilies.

Etymology

French crochet, diminutive of croc, 'hook'

Example

The prolegs of a noctuid moth larva bear crochets arranged in a biordinal mesal penellipse, whereas many geometrid larvae possess only uniordinal crochets in a complete circle.

Synonyms

• hooklets
• proleg hooks

Related Terms

• Proleg
• Sclerite
• Sclerotization
• uniordinal
• biordinal
• Lepidoptera
• caterpillar
• thoracic leg

Usage Notes

Crochets are absent in the few lepidopteran larvae that have lost prolegs (e.g., some inchworms with reduced proleg number) and are not homologous with the claws of thoracic legs. The term is sometimes used loosely for similar hook-like structures in other insect larvae, but in strict usage it refers specifically to lepidopteran proleg armature. Arrangement terminology (uniordinal = one size class; biordinal = two distinct size classes; triordinal = three size classes) is essential for larval identification keys.