Depilation increases while hairiness decreases the risk of drowning: A hitherto unappreciated survival role of setae in woolly bear caterpillars of the moth Lemyra imparilis (Lepidoptera: Noctuoidea: Erebidae)

• Published in: European journal of entomology Vol. 113; no. 1; pp. 130 - 134
• Main Author: MEYER-ROCHOW, V. Benno
• Format: Journal Article
• Language: English
• Published: Ceske Budejovice Institute of Entomology 01.01.2016; Institute of Entomology, Biology Centre, Czech Academy of Science
• Subjects: cuticle; erebidae; floating; Hair; insect setae; Insects; Laboratories; lemyra imparilis; lepidoptera; Roles; Scanning electron microscopy; wettability
• ISSN: 1210-5759; 1802-8829
• DOI: 10.14411/eje.2016.016

This note aims to put on record a hitherto unreported function of caterpillar setae supplementary to those already known. When woolly bear caterpillars of the moth Lemyra imparilis (Butler) have their body hairs removed and are dropped into a bucket of water from a height of 30 cm, they sink immediately. Caterpillars, however, with an intact coat of hairs usually float. This hitherto unreported role of caterpillar setae as life-rafts should depend on a high contact angle θ^sub e^, and thus on the position, density and dimensions of the hairs. An SEM examination of the surface structure of the setae revealed a system of fine grooves and small distally pointing barbs on the hair shaft, which can trap air to support the weight of the insect. Insect setae generally and body hairs of caterpillars in particular are known to possess many functions, but a role as life-rafts for caterpillars in danger of drowning can now be added to the list of possible uses of body hairs.