The influence of surface wettability on the ladybird beetles attachment to solid surfaces

The seven-spotted ladybird beetles Coccinella septempunctata(L.) have a hairy adhesive attachment on the foot. They can walk on different surfaces because of the presence of setae on the foot. The beetles secrete an adhesive secretion on the adhesive pads of their legs. In this paper, the measurements of traction force using seven-spotted ladybird beetles Coccinella septempunctata(L.) were carried out to understand the influence of surface wettability on insect attachment to solid surfaces. The experiments were performed on four smooth substrates with different dynamic (contact angle hysteresis(CA)) dewettabilities toward n-hexadecane: (a) Si substrate modified with a perfluoroalkyl silane (FAS3, CF 3 CH 2 CH 2 Si(OCH 3 ) 3 ) monolayer, (b) Si substrate modified with a perfluoroalkyl silane (FAS13, CF 3 (CF 2 ) 5 CH 2 CH 2 Si(OCH 3 ) 3 ) monolayer, (c) Si substrate modified with a perfluoroalkyl silane (FAS17, CF 3 (CF 2 ) 7 CH 2 CH 2 Si(OCH 3 ) 3 ) monolayer, (d) glass substrate covered with a decyltrietoxysilane (C10, CH 3 (CH 2 ) 9 Si(OC 2 H 5 ) 3 ). Judging from the traction force data achieved on these substrates, the traction force was governed not by the dynamic dewettability (CA hysteresis).