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Attachment ability of male beetles with claws (gray boxes, same data shown in Fig. 3) before washing the substrates in toluene (see Sect. 3.1) and after washing (hatched boxes). Boxplots show the maximum friction forces (a), the corresponding safety factors (b), and the normalized friction forces (c), which were normalized to the 1:10 substrate. Bars with asterisks indicate statistical differences (see Sect. 2.4). Males with and without claws, N = 13
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Many insects possess adhesive foot pads, which enable reliable attachment to diverse and unpredictable substrates. The function of these adhesive organs was shown to be affected by environmental conditions such as substrate roughness, chemistry, and ambient humidity. So far, the attachment ability of insects and also that of spiders and geckos has...
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... To the best of our knowledge, the parasitoid insects tested in the present study are the first species, where sexual dimorphism has been found in the attachment ability to surfaces with different wettability. Sexual dimorphism in insect attachment on smooth and rough surfaces or to stiff and soft substrates has been previously described in Coleoptera (Voigt et al., 2008;Heepe et al., 2017), but it is related to the different morphology of attachment devices, in particular specialised discoidal adhesive tarsal setae enabling males to adhere properly to female elytra during copulation. In the parasitoid species tested in the present investigation, we did not observe any difference in the shape of the arolium between the two sexes. ...
... In common with most beetles from the family Chrysomelidae [37], this species has hairy tarsal adhesive pads (according to [1,38]). Tenent setae of these pads have different shapes of the tip: (1) a flat discoidal terminal element in mushroom-like setae situated in the central part of the basal and distal tarsomeres (only in males, present in all legs); (2) a flat and widened end plate called spatula in setae located around the field of the mushroom-like setae and in the distal part of the middle pad; and (3) showing a distinct sexual dimorphism in structure and attachment performance of adhesive pads [15,17,24,25,[39][40][41][42], as well as on mushroom-shaped contact elements of artificial attachment systems [43,44], revealed a strong adaptation of the discoidal tips to long-term adhesion on smooth substrates, especially needed for firm attachment of males to smooth female elytra during mating. Setae with spatula-shaped or pointed tips are better adapted to short-term temporary adhesion and locomotion on various microrough surfaces. ...
This study focuses on experimental testing of the contamination hypothesis and examines how the contamination of insect adhesive pads with three-dimensional epicuticular waxes of different plant species contributes to the reduction of insect attachment. We measured traction forces of tethered Chrysolina fastuosa male beetles having hairy adhesive pads on nine wax-bearing plant surfaces differing in both shape and dimensions of the wax structures and examined insect adhesive organs after they have contacted waxy substrates. For comparison, we performed the experiments with the same beetle individuals on a clean glass sample just before (gl1) and immediately after (gl2) the test on a plant surface. The tested insects showed a strong reduction of the maximum traction force on all waxy plant surfaces compared to the reference experiment on glass (gl1). After beetles have walked on waxy plant substrates, their adhesive pads were contaminated with wax material, however, to different extents depending on the plant species. The insects demonstrated significantly lower values of both the maximum traction force and the first peak of the traction force and needed significantly longer time to reach the maximum force value in the gl2 test than in the gl1 test. These effects were especially pronounced in cases of the plant surfaces covered with wax projections having higher aspect ratios. The data obtained clearly indicated the impact of waxy plant surfaces on the insect ability to subsequently attach to the clean smooth surface. This effect is caused by the contamination of adhesive pads and experimentally supports the contamination hypothesis.
... Owing to this effect, the grease layer on the female body surface could reduce tarsal adhesion [12,24,25]. Moreover, stiffness, chemistry, texture and humidity of substrates are also known to influence attachment forces [7,9,[26][27][28][29][30][31][32][33][34][35][36][37]. Until now, these effects have been well studied on artificial flat smooth and rough surfaces, but rarely in the context of copulation that never occurs on flat surfaces. ...
... Although they show the typical mating posture of leaf beetles, i.e. the male-above position [46], the G. viridula female has a huge swollen abdomen exposed from the elytra during a reproductive season, and males adhere to the exposed abdomen to mate [47], unlike C. americana, the only other species whose attachment forces were measured on alive females [14]. Considering that substrate material and especially its stiffness plays an important role in attachment [27,28,33], the highly sclerotized elytra compared with the membranous abdominal sternite might affect the attachment ability. Our study aims to address the following questions: (i) Does the sexual dimorphism in tarsal attachment structures affect their adhesion performance in the context of mating behaviour in G. viridula? ...
Green dock beetles Gastrophysa viridula exhibit sexual dimorphism in tarsal attachment setae: females have only pointed, lanceolate and spatula-like setae, while males additionally possess discoidal ones. The sexual dimorphism is probably attributed to the necessity of male discoidal setae to adhere to the smooth back of the female during copulation. We aimed to understand its possible mechanism of attachment with G. viridula. Pull-off forces of both females and males were measured on (i) alive females, (ii) dead and dried females, and (iii) resin replicas of fresh females. The attachment ability tended to increase on dead and replicated female surfaces in both sexes, which indicates that the epicuticular grease layer on the integument of alive intact beetles decreases the attachment. This tendency was prominent in females. The present study clearly showed that in G. viridula discoidal setae enable the males to adhere stronger to female surfaces. The divergent performance found between the sexes differing in their setal composition is probably caused by the stiffness difference between the setae types and by the specific shape of the setal tips. A peculiar reproductive biology in G. viridula is probably attributed to this remarkable divergence of labour in their attachment pads between the sexes.
... For this reason, insects have developed very efficient attachment devices located on their tarsi represented by claws and smooth or hairy pads, supplemented with fluids, which make them able to cope with different slopes and with substrates of varying roughness and wettability (e.g. ref. [11][12][13][14][15][16][17][18][19][20]. ...
ZnO-nanoparticles reduce the attachment ability of the green stinkbug Nezara viridula , a major pest worldwide, by aggregating on insect attachment devices. These findings can help to develop nontoxic pest-control methods that can be alternatives to insecticides.
... However, the influences of mechanical substrate properties on attachment have only been investigated in some other animals so far [cf. 25,26]. Another major functional aspect of an attachment system is its adaptation to different loading conditions. ...
... In principle, both intrinsic structural and material properties of the attachment devices, as well as extrinsic environmental factors (i.e. substrate properties, ambient temperature, humidity) can affect the functioning of biological attachment systems [25,26,[38][39][40][41][42]. For example, the adhesion of the tokay gecko (Gekko gecko) was significantly lower on hydrophobic substrates (OTS-SAM coated glass, CA ≈ 100°) than on a comparable hydrophilic substrate (untreated glass, CA ≈ 50°) under shear stress [43]. ...
... Furthermore, hydrophilic substrates favoured the formation of humidity-induced water layers, which additionally increased the overall attachment due to the involvement of capillary adhesion [43]. On the other hand, the effect of substrate mechanical properties on biological attachment systems was reported from male ladybird beetles (Coccinella septempunctata) through a reversal of the relationship between the stiffnesses of the attachment structures and the substrate [26]. Specifically, a decrease in attachment performance became visible as soon as the stiffness of the setae exceeded the stiffness of the substrate. ...
The ectoparasitic lifestyle of the Mediterranean medicinal leech (Hirudo verbana) requires reliable functioning of its attachment organs (i.e. anterior and posterior suction discs) on multiple habitat- and host-specific surfaces under both normal and shear stresses. In addition to some intrinsic properties of the attachment devices, however, only a few extrinsic factors (e.g. substrate roughness and porosity) have been considered in previous studies on leech suckers. Using centrifugal force experiments, we analysed the attachment performance of H. verbana under different types of loading on artificial substrates differing in porosity and their mechanical properties. Whereas the substrate porosity significantly influenced leech attachment under normal and shear loading, the different mechanical properties did not noticeably affect attachment within the considered parameter limits. Furthermore, suction was confirmed to be the primary attachment mechanism independent of the prevailing loading condition. The question of whether the suction cups of H. verbana are adapted to a specific loading condition could not be answered. In any case, our results again highlight the high functional resilience of leech suckers guaranteeing a successful ectoparasitic lifestyle.
... . The soft sawtooth structure was cast from the metal template with polydimethylsiloxane (PDMS: Sylgard 184 [Dow Corning Corp., Midland, MI, USA]) with a Young's modulus of around 2 MPa[29]. The rigid sawtooth structures were molded from such soft sawtooth structures, which had been produced additionally and were not used further for friction measurements, with epoxy resin (Araldite AW 106 resin and HV953 Hardener [Vantico Pty. ...
Legged locomotion of robots can be greatly improved by bioinspired tribological structures and by applying the principles of computational morphology to achieve fast and energy-efficient walking. In a previous research, we mounted shark skin on the belly of a hexapod robot to show that the passive anisotropic friction properties of this structure enhance locomotion efficiency, resulting in a stronger grip on varying walking surfaces. This study builds upon these results by using a previously investigated sawtooth structure as a model surface on a legged robot to systematically examine the influences of different material and surface properties on the resulting friction coefficients and the walking behavior of the robot. By employing different surfaces and by varying the stiffness and orientation of the anisotropic structures, we conclude that with having prior knowledge about the walking environment in combination with the tribological properties of these structures, we can greatly improve the robot’s locomotion efficiency.
... Due to stress distribution, the resulting attachment force will be drastically reduced, which should promote detachment from the substrate. 19 A further decrease of the substrate stiffness, therefore, may not provide any noticeable benefits. The deformation of the PDMS foam may also lead to water accumulation at the interface between foam and adhesive, since it is completely filled with water. ...
Barnacles are able to effectively adhere to most surfaces underwater. Dewetting of the corresponding surface prior to the release of their permanent adhesive plays an important role in the attachment process. Possibly, a surface that is able to interfere with this process may have exceptional fouling repellence and fouling release abilities. Therefore, open-pored foams made from polydimethylsiloxane (PDMS) were tested together with flat PDMS samples as controls in a 13-week-long field experiment in the Baltic Sea. On a weekly basis, both settlement and fouling density development of the bay barnacle Balanus (=Amphibalanus) improvisus were monitored. The overall settlement was close to zero on PDMS foams and the few attached barnacles were not able to stay on the PDMS foams longer than 1 week after initial settlement. Changes in the stiffness of the PDMS foams did not affect these results. Open-pored PDMS foam systems may be a promising tool in the development of new, innovative antifouling strategies.
... Adhesion often plays an important role in locomotion, prey capture, defence and reproduction (Betz and Kölsch 2004;Brau et al. 2016;Eisner and Aneshansley 2000;Federle et al. 2000;Gorb 2001;Opell 1998;von Byern and Grunwald 2010;Wolff et al. 2014Wolff et al. , 2015bWolff et al. , 2017b. It is a means of attaching built structures, such as cocoons, egg sacs and webs, to environmental structures, such as rocks or plants (Grawe et al. 2014;Hansell 2005;Sahni et al. 2012;Wolff et al. 2017a). As the function and efficiency of adhesive organs and secretions differ between species, it can set the boundaries of an ecological niche by giving access to resources or providing a selective benefit if competing over these resources. ...
... Within the last two decades, numerous research programmes have aimed not only to reveal the function and limitations of adhesive organs and biological glues, often within the framework of biomimicry, but also to gain a better understanding of the species' biology. It has been repeatedly demonstrated that the function of adhesive organs and secretions can be affected by environmental humidity (Amarpuri et al. 2015;Heepe et al. 2016;Huber et al. 2005;Niewiarowski et al. 2008;Piorkowski et al. 2018;Puthoff et al. 2010;Shin et al. 2019;von Byern et al. 2019;Wolff and Gorb 2011), surface roughness (Crawford et al. 2016;England et al. 2016;Schnee et al. 2019;Wolff and Gorb 2012), surface softness (Berglin and Gatenholm 1999;Heepe et al. 2017;Voigt et al. 2019) and surface polarity (Crisp et al. 1985;Grohmann et al. 2014;Schnee et al. 2019). Nearly all of these experiments have been conducted in the lab using standardized artificial substrates. ...
It has been suggested that physical interactions between biological and environmental surfaces may constrain ecological niche spaces. However, the mechanistic understanding of niche formation is frequently limited by the lack of information on the function and variation of these interactions. Here, we hypothesised that two closely related species of orb-web spiders have evolved different adhesion performance of web attachment (i.e. piriform silk) facilitating the occupation of contrasting microhabitats: plants versus rocks. Contrary to our prediction, we found that piriform silk adhesion was equally affected by surface chemistry in both species, with maximal adhesion on surfaces with high surface polarity and an average adhesion loss of 70–75% on low polar surfaces. Spiders did not respond to adhesion losses by increasing the anchor size, despite the repeated failure to attach their web to low polar surfaces. In a natural setting, poor adhesion on low polar surfaces may be mitigated by behavioural means, like the preference to place anchors on corrugated surface features such as leaf edges, or the spinning of multiple anchorages and formation of a bundled anchor line. Thus, microhabitat choice for web-building spiders may be governed by structural properties rather than surface chemistry. These results suggest that the repeatedly demonstrated effects of surface chemistry on bio-adhesion may be ecologically less important than assumed and that the role of behaviour in the evolution of bio-adhesion performance has been underestimated.
... [6,7] royalsocietypublishing.org/journal/rsif J. R. Soc. Interface 17: 20200300 attachment ability [65,66]. Moreover, studies on the soft-bodied caterpillars of the tobacco hornworm, Manduca sexta L. (Lepidoptera, Sphingidae), revealed that substrate stiffness can be an essential component of a mechanical system in terms of locomotion (i.e. ...
Haematophagous ectoparasites must ensure a reliable hold to their host during blood meals and, therefore, have evolved a broad spectrum of versatile and effective attachment mechanisms. The Mediterranean medicinal leech (Hirudo verbana), for example, uses suction on both smooth and textured air-tight substrates. However, preliminary studies showed that H. verbana is also capable of attaching itself to air-permeable substrates, where suction does not work. Using high-speed videography and mechanical tests, we comparatively investigated the attachment of H. verbana on both smooth and textured air-tight as well as on porous artificial substrates, also considering the influence of mucus on sucker surfaces. In general, the leech-specific locomotion cycle did not differ between the tested surfaces, and the leeches were able to reliably attach to both air-tight and porous substrates. From our results, we conclude that suction is presumably the primary attachment mechanism of H. verbana. However, secondary mechanisms such as mechanical interlocking with surface asperities and pores or capillary forces occurring at the interface between the mucus-covered suckers and the substratum are also employed. In any case, the rich repertoire of applicable attachment principles renders the organs of H. verbana functionally highly resilient.
... Although it has not been formally tested now, partial insects, such as ants and cockroaches, are suspected after using their antennas to imitate aspects of looking at the Earth before walking in relation to the substrate [10]. Antennas can indeed determine the environment of ants, such as air flow, chemical signal, or the detection of mechanical fragility; thus far they have been proposed in accordance with a bad-fiction and fantasy balance [11]. Both types around the approval implementation pads including surface asperities in mimic the host love to the greatest extent according to surfaces (Figure 1). ...
