Meeting Abstract
P3.177 Tuesday, Jan. 6 Absorption Hypothesis: Attachment of Beetles to Nano-Porous Substrates GORB, E.V.*; HOSODA, N.; GORB, S.N.; MPI for Metals Research, Stuttgart, Germany; NIMS, Tsukuba, Japan; Univ. of Kiel, Germany o.gorb@mf.mpg.de
It has been repeatedly reported that microstructured waxy surfaces of plants strongly reduce insect attachment. To explain anti-adhesive properties of such plant substrates, four hypotheses were previously proposed. Recently, only the two first hypotheses (roughness hypothesis contamination hypothesis) and were proven. The aim of this study was to test the third, fluid absorption hypothesis, claiming that the structured wax coverage may absorb the fluid from the setal surface of insect adhesive pads and by this reduce the adhesion force. Traction force measurements were performed with tethered seven-spotted ladybird beetles Coccinella septempunctata L. (Coleoptera, Coccinellidae), walking on five different substrates: (1) smooth glass plate; (2) smooth solid Al2O3 (sapphire) disc; (3 – 5) porous Al2O3 discs (anodisc membranes, back side) with the same pore diameter (220 – 235 nm), but different porosity (28, 42 and 51%). The force ranged from 0.16 to 16.59 mN in males and from 0.32 to 8.99 mN in females. The highest force values were obtained on the smooth surfaces, where males generated considerably higher forces compared to females. On all three porous substrates, forces were significantly reduced, and the only difference for surfaces was obtained between anodisc membranes with the highest and lowest porosity. Males produced essentially lower forces than females on porous samples. The reduction of insect attachment on anodisc membranes may be explained by (1) possible absorption of the secretory fluid from insect pads by porous media and (2) surface roughness, reducing real contact area between tenent setae and substrate.
