Locomotion in a sticky terrain

Abstract

The mirid bug Pameridea roridulae lives mutalistically on the protocarnivorous plant Roridula gorgonias. The latter resembles an effective, three-dimensional flypaper trap which captures numerous flying insects. We have recently shown that P. roridulae bugs are not trapped by the plant, because they are covered with a layer of epicuticular grease, which is considerably thicker than in other insects. The present study demonstrates that the bugs' morphology and locomotory characteristics also contribute to their specialisation for life on the adhesive plant surface. A structural analysis of the mirid bug's attachment system, and an experimental study on its attachment ability were carried out. In traction force tests, maximum forces of 8.8 mN were measured on adaxial R. gorgonias leaves, corresponding to 126 times the bug's body weight. On smooth surfaces, generated forces were only 47 times the bug's body weight. Compared to closely related mirid bug species avoiding contact with plant adhesive secretion, P. roridulae is distinctly stronger and heavier, and holds its body close to the plant substrate. Two locomotion strategies on the glandular hairy plant surfaces are suggested for mirid bug species from the tribus Dicyphini: (1) avoidance strategy, characterised by the slim body held at a large distance from the plant surface by using long, slender legs, and (2) defense strategy, where trapping of the heavy bugs, situated close to the plant surface, is overcome by generating strong forces during locomotion and by having a thick anti-adhesive epicuticular greasy layer on the bugs' cuticle.

Leaf beetle attachment on wrinkles: isotropic friction on anisotropic surfaces

“…The direct influence of different plant surface characteristics on insect attachment has been experimentally shown previously for representatives of Coleoptera: Chrysomelidae (Stork, 1980b;Stork, 1980c;Gorb and Gorb, 2002;Gorb and Gorb, 2006;Gorb and Gorb, 2009), Coccinellidae Gorb and Gorb, 2011), Staphylinidae (Betz, 2002); Diptera: Calliphoridae Gorb et al, 2004), Drosophilidae (Gaume et al, 2002); Hemiptera: Aphididae (Lees and Hardie, 1988), Pyrrhocoridae , Miridae (Voigt et al, 2007;Voigt and Gorb, 2010); and Hymenoptera: Formicidae (Federle et al, 1997;Federle et al, 2000;Gaume et al, 2002). Nano-rough plant surfaces covered with wax crystals were reported to prevent attachment in the majority of investigated insect species.…”

“…The structure and performance of tarsal attachment devices in both beetle species have previously been well studied (e.g. Peressadko and Gorb, 2004;Schuppert et al, 2005;Voigt et al, 2008;Voigt et al, 2010;Gorb and Gorb, 2009;Bullock and Federle, 2009;Bullock and Federle, 2011;Clemente et al, 2010;Hosoda and Gorb, 2011;Prüm et al, 2012). Both species bear spatula-shaped lanceolate and filament-shaped tarsal adhesive setae in males and females, and additionally setae with discoid terminal tips only in males (Stork, 1980a;Pelletier and Smilowitz, 1987).…”

Locomotion and attachment of leaf beetle larvaeGastrophysa viridula(Coleoptera, Chrysomelidae)

“…However, young larvae are more often found on the underside of the leaves while adults do not show such a preference [67]. Adaxial and abaxial leaf surfaces have different surface roughness owing to the stronger presence of stomata and trichomes, and pronounced venation on the abaxial side [11,68,69]. Hosoda & Gorb [70] showed greater attachment ability of adult beetles to the adaxial than the abaxial side of dock leaves (R. obtusifolius) [70].…”

Do plant trichomes cause more harm than good to predatory insects?

“…In addition, P . roridulae generates considerable force/energy – it has a relatively heavy body – to move along the surface of the leaves of the plant without entrapment …”