Eur. J. Entomol. 113: 130-134, 2016 | 10.14411/eje.2016.016

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)

V. Benno MEYER-ROCHOW1,2
1 Department of Genetics and Physiology, Oulu University, Oulu, FIN 90140, Finland; e-mail: victor.benno@oulu.fi
2 Research Institute of Luminous Organisms, Hachijo Island, 2872 Nakanogo, Hachijojima, Tokyo 100-1623, Japan; e-mail: vbmeyrow@gmail.com

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 θe, 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.

Keywords: Lepidoptera, Erebidae, Lemyra imparilis, insect setae, cuticle, wettability, floating

Received: October 26, 2015; Accepted: January 4, 2015; Published online: January 28, 2016

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