Naoe Hosoda

Slippery pores: anti-adhesive effect of nanoporous substrates on the beetle attachment system

Traction experiments with adult seven-spotted ladybird beetles Coccinella septempunctata (L.) were carried out to study the influence of surface structure on insect attachment. Force measurements were performed with tethered walking insects, both males and females, on five different substrates: (i) smooth glass plate, (ii) smooth solid Al2O3 (sapphire) disc, and (iii–v) porous Al2O3 discs (anodisc membranes) with the same pore diameter but different porosity. The traction force of beetles ranged from 0.16 to 16.59 mN in males and from 0.32 to 8.99 mN in females. In both sexes, the highest force values were obtained on smooth solid surfaces, where males showed higher forces than females. On all three porous substrates, forces were significantly reduced in both males and females, and the only difference within these surfaces was obtained between membranes with the highest and lowest porosity. Males produced essentially lower forces than females on porous samples. The reduction in insect attachment on anodisc membranes may be explained by (i) possible absorption of the secretion fluid from insect adhesive pads by porous media and/or (ii) the effect of surface roughness. Differences in attachment between males and females were probably caused by the sexual dimorphism in the terminal structure of adhesive setae.

Underwater locomotion in a terrestrial beetle: combination of surface de-wetting and capillary forces

For the first time, we report the remarkable ability of the terrestrial leaf beetle Gastrophysa viridula to walk on solid substrates under water. These beetles have adhesive setae on their feet that produce a secretory fluid having a crucial role in adhesion on land. In air, adhesion is produced by capillary forces between the fluid-covered setae and the substrate. In general, capillary forces do not contribute to adhesion under water. However, our observations showed that these beetles may use air bubbles trapped between their adhesive setae to walk on flooded, inclined substrata or even under water. Beetle adhesion to hydrophilic surfaces under water was lower than that in air, whereas adhesion to hydrophobic surfaces under water was comparable to that in air. Oil-covered hairy pads had a pinning effect, retaining the air bubbles on their feet. Bubbles in contact with the hydrophobic substrate de-wetted the substrate and produced capillary adhesion. Additional capillary forces are generated by the pads liquid bridges between the foot and the substrate. Inspired by this idea, we designed an artificial silicone polymer structure with underwater adhesive properties.

Friction force reduction triggers feet grooming behaviour in beetles.

In insects, cleaning (grooming) of tarsal attachment devices is essential for maintaining their adhesive ability, necessary for walking on a complex terrain of plant surfaces. How insects obtain information on the degree of contamination of their feet has remained, until recently, unclear. We carried out friction force measurements on walking beetles Gastrophysa viridula (Coleoptera, Chrysomelidae) and counted grooming occurrence on stiff polymer substrata with different degrees of nanoroughness (root mean square: 28–288 nm). Since nanoscopically, rough surfaces strongly reduced friction and adhesion without contaminating feet, we were able to demonstrate, for the first time to our knowledge, that friction force between tarsal attachment pads and the substrate provides an insect with information on the degree of contamination of its attachment structures. We have shown that foot grooming occurrence correlates not only with the degree of contamination but also with the decrease of friction force. This result indicates that insects obtain information about the degree of contamination, not statically but rather dynamically and, presumably, use mechanoreceptors monitoring either tensile/compressive forces in the cuticle or tensile forces between leg segments.

Morphology and microstructure of the Ar+ion sputtered (0001)α-Al2O3 surface

Abstract The morphology and microstructure of Ar+-ion bombarded (0001) α-Al2O3 surfaces were studied by employing analytical electron microscopy (AEM) and high-resolution transmission electron microscopy (HRTEM). Surface bombardment with 1 keV Ar+-ions resulted in the formation of a ca. 3-nm thick γ-Al2O3 layer with a high density of structural defects. A well-defined epitaxial orientation relationship between the γ-Al2O3 layer and the substrate was observed: (0001)α ∥(111)γ, [10 1 0]α ∥[110]γ, and [11 2 0]α ∥±[11 2 ]γ.

On the laboratory rearing of green dock leaf beetles Gastrophysa viridula (Coleoptera: Chrysomelidae): Laboratory rearing of Gastrophysa viridula

Abstractu2002 Leaf beetles Gastrophysa viridula have attracted recently increased research interest from various points of view, since they are: (i) pest insects in rhubarb crops; (ii) potential biocontrol agents of dock plants Rumex spp. in grasslands; and (iii) a model species in ecological studies on insect population dynamics, biochemistry, behavior, biomechanics and biomimetics. The continuous rearing of beetles at standardized conditions may help to unify the fitness state of different individuals, allowing a better comparison of experimental results. The present communication suggests a modular space‐ and time‐saving rearing method of G. viridula in stackable faunariums under laboratory conditions, which has been successfully established and continuously used over the last 5 years. Several developmental stages were kept in separate boxes, and multiple generations were kept simultaneously, depending on the required number of beetles.

Nano-porous substrates reduce beetle attachment force

Traction experiments with the seven-spotted ladybird beetles Coccinella septempunctata (L.) (Coleoptera, Coccinellidae) were carried out to study the influence of surface structure on insect attachment. Force measurements were performed with tethered walking insects using a load cell force transducer. For each beetle, forces were measured on five different substrates: (1) smooth glass plate; (2) smooth solid Al2 O3 (sapphire) disc; (3 – 5) porous Al2 O3 discs (anodiscs, back side) with the same pore diameter (220 – 235 nm), but different porosity (28, 42 and 51%). Males (N = 10) and females (N = 10) were used in experiments (10 single runs on each surface). Additionally, inversion tests were performed after each traction force measurement. The force ranged from 0.368 to 10.370 mN in males and from 0.514 to 6.262 mN in females. In both sexes, the highest force values were obtained on the smooth glass and sapphire surfaces, where males generated considerably higher forces compared to females. On all three porous substrates, forces were significantly reduced in both males and females, and the only difference for surfaces was obtained between two extremes: anodiscs with the highest (51%) and lowest (28%) porosity. Males produced essentially lower forces than females on anodiscs samples. Experimental insects performed well and showed normal locomotion on both smooth surfaces. On all anodiscs samples, beetles usually were not able to get a grip and slid over the surface, refused to walk and came to a standstill or even turned over on their backs. When substrates were inverted to 90° and 180°, insects were still able to remain attached to both the glass and sapphire samples, but failed on anodiscs. The reduction of insect attachment on anodiscs surfaces is explained by (1) possible absorption of the secretory fluid from insect pads by porous media and (2) effect of surface roughness.Copyright