Influence of ambient humidity on the attachment ability of ladybird beetles (Coccinella septempunctata).
Many insects possess adhesive foot pads, which enable them to scale smooth vertical surfaces. The function of these organs may be highly affected by environmental conditions. Ladybird beetles (Coccinellidae) possess dense tarsal soles of tenent setae, supplemented with an adhesive fluid. We studied the attachment ability of the seven-spotted ladybird beetle (Coccinella septempunctata) at different humidities by horizontal traction experiments. We found that both low (15%) and high (99%) relative humidities lead to a decrease of attachment ability. The significantly highest attachment forces were revealed at 60% humidity. This relationship was found both in female and male beetles, despite of a deviating structure of adhesive setae and a significant difference in forces between sexes. These findings demonstrate that not only dry adhesive setae are affected by ambient humidity, but also setae that stick due to the capillarity of an oily secretion.
Department of Functional Morphology and Biomechanics, Kiel University, Am Botanischen Garten 1-9, D-24118 Kiel, Germany.|Mads Clausen Institute, University of Southern Denmark, NanoSYD Alsion 2, 6400 Sønderborg, Denmark.
Lars
L
Heepe
Department of Functional Morphology and Biomechanics, Kiel University, Am Botanischen Garten 1-9, D-24118 Kiel, Germany.|Department of Biological Sciences, Macquarie University, Sydney, NSW 2109, Australia.
Jonas O
JO
Wolff
Department of Functional Morphology and Biomechanics, Kiel University, Am Botanischen Garten 1-9, D-24118 Kiel, Germany.
Stanislav N
SN
Gorb
adhesion; beetle; biomechanics; force measurement; friction; insect; locomotion; surface