The radula is a crucial adaptation for food-processing in molluscs.A deeper understanding of the interaction between the radula and the preferred food is lacking,complicating the inference of the precise ecological ro...The radula is a crucial adaptation for food-processing in molluscs.A deeper understanding of the interaction between the radula and the preferred food is lacking,complicating the inference of the precise ecological roles of radular structures.This study presents the first experimental set-up that allows to study the influence of the radular morphology,specifically the degree of tooth-tooth interlocking(so-called collective effect),on the feeding efficiency.For this purpose,physical 3D models of the teeth were designed using CAD software and 3D printing technique.The feeding efficiencies with models of different degree of interlocking were determined by tensile tests,pulling the models trough agar gels with different viscosities.The forces generated by the models and the masses of the removed gel fragments were determined.We found,that radular models with a high degree of tooth–tooth interlocking performed best as they were able to remove most agar.We additionally broke the teeth and determined,that the teeth with the highest degree of interlocking could resist to highest force.Overall,the study highlights the complex interplay between radular morphology and its ecological function,suggesting that even minor morphological alterations can significantly impact the efficiency and effectiveness of food gathering.Understanding these interactions cannot only shed light on the ecological adaptations of molluscs,but provide further insights into development of more effective grinding,scraping,and cleaning technical devices.展开更多
Flight feathers of birds interact with the air flow during flight.How the observed low drag and high lift values at wind speeds from 9.0 to 19.8 m/s can be achieved due to the feather aerodynamics remains unknown.In t...Flight feathers of birds interact with the air flow during flight.How the observed low drag and high lift values at wind speeds from 9.0 to 19.8 m/s can be achieved due to the feather aerodynamics remains unknown.In the present paper,we tested and compared morphological changes,drag reduction and flow visualization results of intact,damaged,and artificial feathers at different wind speeds in a wind tunnel.Through the analysis of the drag force and resultant force angle,we proved that the integrity of feathers,whose barbs are usually closely interconnected,played an important role in the drag,which potentially triggers excellent drag reduction performance.The wind tunnel tests indicated that intact secondary feathers had a surprisingly high maximum drag reduction property at v?=?9 m/s compared with the feathers,where the integrity of barbs was damaged.The hook cascades facilitated elasticity under pressure and suitable permeability in an intact feather,when the hooks were interlocked.It was indicated that the suitable permeability of intact feathers would prevent flow separation and reduce drag force at low wind speed;at high wind speed,elasticity under pressure and suitable permeability in an intact feather would facilitate strong squeezing effect,helping feathers withstand larger aerodynamic forces to which they might be subjected during flight.It was revealed that the intact secondary feather is a compromise between strong lift generation and drag reduction,which has a great significance for the bird’s flight.展开更多
This paper presents a learning-based control framework for fast(<1.5 s)and accurate manipulation of a flexible object,i.e.,whip targeting.The framework consists of a motion planner learned or optimized by an algori...This paper presents a learning-based control framework for fast(<1.5 s)and accurate manipulation of a flexible object,i.e.,whip targeting.The framework consists of a motion planner learned or optimized by an algorithm,Online Impedance Adaptation Control(OIAC),a sim2real mechanism,and a visual feedback component.The experimental results show that a soft actor-critic algorithm outperforms three Deep Reinforcement Learning(DRL),a nonlinear optimization,and a genetic algorithm in learning generalization of motion planning.It can greatly reduce average learning trials(to<20 of others)and maximize average rewards(to>3 times of others).Besides,motion tracking errors are greatly reduced to 13.29 and 22.36 of constant impedance control by the OIAC of the proposed framework.In addition,the trajectory similarity between simulated and physical whips is 89.09.The presented framework provides a new method integrating data-driven and physics-based algorithms for controlling fast and accurate arm manipulation of a flexible object.展开更多
Bird feathers sustain bending and vibrations during flight.Such unwanted vibrations could potentially cause noise and flight instabilities.Damping could alter the system response,resulting in improving quiet flight,st...Bird feathers sustain bending and vibrations during flight.Such unwanted vibrations could potentially cause noise and flight instabilities.Damping could alter the system response,resulting in improving quiet flight,stability,and controllability.Vanes of feathers are known to be indispensable for supporting the aerodynamic function of the wings.The relationship between the hierarchical structures of vanes and the mechanical properties of the feather has been previously studied.However,still little is known about their relationship with feathers’damping properties.Here,the role of vanes in feathers’damping properties was quantified.The vibrations of the feathers with vanes and the bare shaft without vanes after step deflections in the plane of the vanes and perpendicular to it were measured using high-speed video recording.The presence of several main natural vibration modes was observed in the feathers with vanes.After trimming vanes,more vibration modes were observed,the fundamental frequencies increased by 51-70%,and the damping ratio decreased by 38-60%.Therefore,we suggest that vanes largely increase feather damping properties.Damping mechanisms based on the morphology of feather vanes are discussed.The aerodynamic damping is connected with the planar vane surface,the structural damping is related to the interlocking between barbules and barbs,and the material damping is caused by the foamy medulla inside barbs.展开更多
Water striders inhabit the elastic surface tension film of water, sharing their environment with other aquatic organisms. Their survival relies heavily on swift maneuverability and navigation around floating obstacles...Water striders inhabit the elastic surface tension film of water, sharing their environment with other aquatic organisms. Their survival relies heavily on swift maneuverability and navigation around floating obstacles, which aids in the exploration of their habitat and in escaping from potential threats. Their high agility is strongly based on the ability to execute precise turns, enabling effective directional control. This paper investigates the intricate coordination of leg movements essential for initiating and sustaining turning maneuvers in water striders. We elucidate the distinct roles of each leg in modulating posture and stability during turns, with a focus on the pivotal role of the midlegs in maintaining directional movement. Through analysis of leg accelerations, decelerations, and load distribution, we unveil the spatiotemporal dynamics governing successful turns. Our findings reveal refined turning strategies employed by water striders in varying situations, from narrow to wide turns, characterized by adaptations in their locomotor system, particularly in the widening of the sculling field. Additionally, we report the phenomenon of reverse sculling, a novel escape tactic of water striders. By shedding light on the maneuverability of water striders, this study contributes to a deeper understanding of animal locomotion strategies in aquatic environments.展开更多
In the course of their evolution,insects developed diverse supplementary structures on their legs to enable them to grip a variety of substrata.Sufficient grip is required to generate propulsive forces by friction or/...In the course of their evolution,insects developed diverse supplementary structures on their legs to enable them to grip a variety of substrata.Sufficient grip is required to generate propulsive forces by friction or/and interlocking with the substrate during locomotion.Highly specialized adhesive organs provide a mechanism of attachment to relatively smooth surfaces.Additionally,insect legs are supplemented by rather sharp-pointed claws and tibial spurs,which are structures adapted to interact with diverse rough textures.From a biomechanical perspective,one single claw terminating the tarsus would be sufficient for generating a grip on rough substrates.Interestingly,the majority of insects and spiders possess paired claws at the pretarsus,which is rather difficult to explain for tribological reasons.Using numerical modeling,this paper studies the attachment forces generated by gripping systems consisting of different numbers of claws on the craterous substrate texture.A numerical model is studied based on elastically connected shells constructed using movable digital automata and a numerically generated random surface.The solitary claw is not the optimal solution because of the instability of its motion along the peculiarities of the random terrain.A systematic study of the sequence of numerical simulations reveals that the optimal number of claws is between two and three,with a slight preference for two.This conclusion is drawn from direct qualitative observations of the numerically simulated dynamic scenarios and quantitative calculations of the forces and other values obtained from the simulations.展开更多
Insects can adapt their walking patterns to complex and varied environments and retain the ability to walk even after significant changes in their physical attributes,such as amputation.Although the interleg coordinat...Insects can adapt their walking patterns to complex and varied environments and retain the ability to walk even after significant changes in their physical attributes,such as amputation.Although the interleg coordination of intact insects has been widely described in previous studies,the adaptive walking patterns in free-walking insects with amputation of 1 or more legs are still unclear.The pentatomid bug Erthesina fullo exhibits a tripod gait,when walking freely on horizontal substrates,like many other insects.In this study,amputations were performed on this species to investigate changes in interleg coordination.The walking parameters were analyzed,such as the locations of touchdown and liftoff,cycle period,walking speed,and head displacement of intact and amputated insects.The results show that E.fullo displays adaptive interleg coordination in response to amputations.With 1 amputated leg,bugs changed to a 3-unit gait,whereas with 2 amputated legs they employed a wave gait.These data are helpful in exploring the motion mode control in walking insects and provide the theoretical basis for the gait control strategy of robots,when leg failure occurs.展开更多
Scorpions are distributed almost all over the world and inhabit rainforests,deserts,mountains,and littoral zones.Their multifunctional chelae play a key role in their biology.The chela is the pincer that has originate...Scorpions are distributed almost all over the world and inhabit rainforests,deserts,mountains,and littoral zones.Their multifunctional chelae play a key role in their biology.The chela is the pincer that has originated from the last two segments of the pedipalp.Many previous studies have focused on the morphology of the chela and the overall pincer force.The knowledge about the material properties of scorpion chelae remains rather poor.In particular,little is known about the spines located on the grasping edge of the chela.In this study,we use a combination of nanoindentation,micro-computer tomography,confocal laser scanning microscopy,scanning electron microscopy and energy-dispersive X-ray elemental analysis,to examine the mechanical properties,relative density,sclerotization level,microstructure and biomineralization of both the regular cuticle and the spine cuticle of the chela in the scorpion Androctonus bicolor.Our results show that the mechanical property values of the spine cuticle are significantly higher than those of the regular cuticle.This can reduce the risk of damage to the chela,increase the chance of indentation into the prey tissue and is very likely to result from both higher sclerotization level and biomineralization due to the accumulation of zinc.The specialized microstructure of the cuticle could contribute to the enhancement of the stiffness,strength and toughness of the chela.This study aids in better understanding the material structure,composition and properties of the scorpion chela cuticle.展开更多
Living organisms,such as geckos and insects,exhibit excellent climbing ability on various complex surfaces due to the hair-like hierarchical adhesive systems of their attachment devices.Over the past few decades,an in...Living organisms,such as geckos and insects,exhibit excellent climbing ability on various complex surfaces due to the hair-like hierarchical adhesive systems of their attachment devices.Over the past few decades,an increased understanding of the mechanisms of multiscale hierarchical adhesion systems and the continual improvement of theoretical modeling have promoted the rapid advancement in the design and application of biomimetic artificial adhesives.The modeling of biomimetic artificial adhesives has developed from simple structures to complex constructions with multilevel hierarchical properties.A review of advances in the development of these contact mechanics models is presented here.Adhesion and friction models considering multiscale hierarchical structural forms are discussed,with a focus on multiscale hierarchical models based on the development of the Cantor‒Borodich profiles.Finally,the most recent developments in studies of artificial setae with spatula-like ends,both axisymmetric and non-axisymmetric,are reviewed.展开更多
The ability to fly is crucial for migratory insects.Consequently,the accumulation of damage on the wings over time can affect survival,especially for species that travel long distances.We examined the frequency of irr...The ability to fly is crucial for migratory insects.Consequently,the accumulation of damage on the wings over time can affect survival,especially for species that travel long distances.We examined the frequency of irreversible wing damage in the migratory butterfly Vanessa cardui to explore the effect of wing structure on wing damage frequency,as well as the mechanisms that might mitigate wing damage.An exceptionally high migration rate driven by high precipitation levels in their larval habitats in the winter of 2018–2019 provided us with an excellent opportunity to collect data on the frequency of naturally occurring wing damage associated with long-distance flights.Digital images of 135 individuals of V.cardui were collected and analyzed in Germany.The results show that the hindwings experienced a greater frequency of damage than the forewings.Moreover,forewings experienced more severe damage on the lateral margin,whereas hindwings experienced more damage on the trailing margin.The frequency of wing margin damage was higher in the painted lady butterfly than in the migrating monarch butterfly and in the butterfly Pontia occidentalis following artificially induced wing collisions.The results of this study could be used in future comparative studies of patterns of wing damage in butterflies and other insects.Additional studies are needed to clarify whether the strategies for coping with wing damage differ between migratory and nonmigratory species.展开更多
Tribological properties of femoro-tibial leg joints in two beetles,darkling beetle Zophobas morio and Congo rose chafer Pachnoda marginata were studied.Very low friction of 0.004 was revealed by the direct measurement...Tribological properties of femoro-tibial leg joints in two beetles,darkling beetle Zophobas morio and Congo rose chafer Pachnoda marginata were studied.Very low friction of 0.004 was revealed by the direct measurements in the joint.It is assumed that semi-solid lubricant functioning as in technical bearings is one of the leading factors of the friction minimization.Dependence of the surface texture and physical chemical properties(hydrophobicity)on the cuticle friction was analysed.Contribution of the surface texture to the tribological properties of contacting surfaces was examined by the measurement in the tribosystem“contacting surface/glass”.It is supposed that coefficient of friction(COF)decreases with decrease of surface roughness.At the same time,no statistically significant correlation was found between the hydrophobicity of the surface and the value of the friction coefficient.展开更多
Geometric and micro-structure design, tribology properties of beetle joints were experimentally studied, which aimed to enlighten ideas for the joint design of MEMS.The observation by using SEM and microscopy suggeste...Geometric and micro-structure design, tribology properties of beetle joints were experimentally studied, which aimed to enlighten ideas for the joint design of MEMS.The observation by using SEM and microscopy suggested that beetle's joints consist of a concave surface matched with a convex surface. The heads of the beetles, rubbing with flat glass, were tested in fresh and dried statuses and compared with sapphire ball with flat glass. Frictional coefficient of the joint material on glass was significantly lower than that of the sapphire sphere on glass. The material of the joint cuticle for convex surface is rather stiff (the elastic modulus 4.5 Gpa) and smooth. The surface is hydrophobic (the contact angle of distilled water was 88.3° ). It is suggested here that the high stiffness of the joint material and hydrophobicity of the joint surface are parts of the mechanism minimizing friction in insect joints.展开更多
基金Open Access funding enabled and organized by Projekt DEALfinanced by the Deutsche Forschungsgemeinschaft(DFG)grant 470833544 to WK.
文摘The radula is a crucial adaptation for food-processing in molluscs.A deeper understanding of the interaction between the radula and the preferred food is lacking,complicating the inference of the precise ecological roles of radular structures.This study presents the first experimental set-up that allows to study the influence of the radular morphology,specifically the degree of tooth-tooth interlocking(so-called collective effect),on the feeding efficiency.For this purpose,physical 3D models of the teeth were designed using CAD software and 3D printing technique.The feeding efficiencies with models of different degree of interlocking were determined by tensile tests,pulling the models trough agar gels with different viscosities.The forces generated by the models and the masses of the removed gel fragments were determined.We found,that radular models with a high degree of tooth–tooth interlocking performed best as they were able to remove most agar.We additionally broke the teeth and determined,that the teeth with the highest degree of interlocking could resist to highest force.Overall,the study highlights the complex interplay between radular morphology and its ecological function,suggesting that even minor morphological alterations can significantly impact the efficiency and effectiveness of food gathering.Understanding these interactions cannot only shed light on the ecological adaptations of molluscs,but provide further insights into development of more effective grinding,scraping,and cleaning technical devices.
基金This work was supported by the Chinesisch-Deutsches Zentrumfur Wissenschaftsforderung to SNG and ZDD(Grant No.GZl154)the National Natural Science Foundation of China(Grant Nos.51875281,51861135306)。
文摘Flight feathers of birds interact with the air flow during flight.How the observed low drag and high lift values at wind speeds from 9.0 to 19.8 m/s can be achieved due to the feather aerodynamics remains unknown.In the present paper,we tested and compared morphological changes,drag reduction and flow visualization results of intact,damaged,and artificial feathers at different wind speeds in a wind tunnel.Through the analysis of the drag force and resultant force angle,we proved that the integrity of feathers,whose barbs are usually closely interconnected,played an important role in the drag,which potentially triggers excellent drag reduction performance.The wind tunnel tests indicated that intact secondary feathers had a surprisingly high maximum drag reduction property at v?=?9 m/s compared with the feathers,where the integrity of barbs was damaged.The hook cascades facilitated elasticity under pressure and suitable permeability in an intact feather,when the hooks were interlocked.It was indicated that the suitable permeability of intact feathers would prevent flow separation and reduce drag force at low wind speed;at high wind speed,elasticity under pressure and suitable permeability in an intact feather would facilitate strong squeezing effect,helping feathers withstand larger aerodynamic forces to which they might be subjected during flight.It was revealed that the intact secondary feather is a compromise between strong lift generation and drag reduction,which has a great significance for the bird’s flight.
基金supported in part by the Brødrene Hartmanns(No.A36775)Thomas B.Thriges(No.7648-2106)+1 种基金Fabrikant Mads Clausens(No.2023-0210)EnergiFyn funds.
文摘This paper presents a learning-based control framework for fast(<1.5 s)and accurate manipulation of a flexible object,i.e.,whip targeting.The framework consists of a motion planner learned or optimized by an algorithm,Online Impedance Adaptation Control(OIAC),a sim2real mechanism,and a visual feedback component.The experimental results show that a soft actor-critic algorithm outperforms three Deep Reinforcement Learning(DRL),a nonlinear optimization,and a genetic algorithm in learning generalization of motion planning.It can greatly reduce average learning trials(to<20 of others)and maximize average rewards(to>3 times of others).Besides,motion tracking errors are greatly reduced to 13.29 and 22.36 of constant impedance control by the OIAC of the proposed framework.In addition,the trajectory similarity between simulated and physical whips is 89.09.The presented framework provides a new method integrating data-driven and physics-based algorithms for controlling fast and accurate arm manipulation of a flexible object.
基金financially supported by Sino-German Center for Research Promotion (Grant no.GZ1154).
文摘Bird feathers sustain bending and vibrations during flight.Such unwanted vibrations could potentially cause noise and flight instabilities.Damping could alter the system response,resulting in improving quiet flight,stability,and controllability.Vanes of feathers are known to be indispensable for supporting the aerodynamic function of the wings.The relationship between the hierarchical structures of vanes and the mechanical properties of the feather has been previously studied.However,still little is known about their relationship with feathers’damping properties.Here,the role of vanes in feathers’damping properties was quantified.The vibrations of the feathers with vanes and the bare shaft without vanes after step deflections in the plane of the vanes and perpendicular to it were measured using high-speed video recording.The presence of several main natural vibration modes was observed in the feathers with vanes.After trimming vanes,more vibration modes were observed,the fundamental frequencies increased by 51-70%,and the damping ratio decreased by 38-60%.Therefore,we suggest that vanes largely increase feather damping properties.Damping mechanisms based on the morphology of feather vanes are discussed.The aerodynamic damping is connected with the planar vane surface,the structural damping is related to the interlocking between barbules and barbs,and the material damping is caused by the foamy medulla inside barbs.
文摘Water striders inhabit the elastic surface tension film of water, sharing their environment with other aquatic organisms. Their survival relies heavily on swift maneuverability and navigation around floating obstacles, which aids in the exploration of their habitat and in escaping from potential threats. Their high agility is strongly based on the ability to execute precise turns, enabling effective directional control. This paper investigates the intricate coordination of leg movements essential for initiating and sustaining turning maneuvers in water striders. We elucidate the distinct roles of each leg in modulating posture and stability during turns, with a focus on the pivotal role of the midlegs in maintaining directional movement. Through analysis of leg accelerations, decelerations, and load distribution, we unveil the spatiotemporal dynamics governing successful turns. Our findings reveal refined turning strategies employed by water striders in varying situations, from narrow to wide turns, characterized by adaptations in their locomotor system, particularly in the widening of the sculling field. Additionally, we report the phenomenon of reverse sculling, a novel escape tactic of water striders. By shedding light on the maneuverability of water striders, this study contributes to a deeper understanding of animal locomotion strategies in aquatic environments.
基金Funding to Stanislav N.Gorb by the grant GO 995/34-2 within the SPP 2100 Soft Material Robotics from the German Science Foundation(DFG)is acknowledged.
文摘In the course of their evolution,insects developed diverse supplementary structures on their legs to enable them to grip a variety of substrata.Sufficient grip is required to generate propulsive forces by friction or/and interlocking with the substrate during locomotion.Highly specialized adhesive organs provide a mechanism of attachment to relatively smooth surfaces.Additionally,insect legs are supplemented by rather sharp-pointed claws and tibial spurs,which are structures adapted to interact with diverse rough textures.From a biomechanical perspective,one single claw terminating the tarsus would be sufficient for generating a grip on rough substrates.Interestingly,the majority of insects and spiders possess paired claws at the pretarsus,which is rather difficult to explain for tribological reasons.Using numerical modeling,this paper studies the attachment forces generated by gripping systems consisting of different numbers of claws on the craterous substrate texture.A numerical model is studied based on elastically connected shells constructed using movable digital automata and a numerically generated random surface.The solitary claw is not the optimal solution because of the instability of its motion along the peculiarities of the random terrain.A systematic study of the sequence of numerical simulations reveals that the optimal number of claws is between two and three,with a slight preference for two.This conclusion is drawn from direct qualitative observations of the numerically simulated dynamic scenarios and quantitative calculations of the forces and other values obtained from the simulations.
基金supported by the National Natural Science Foundation of China under Grant 52075248,Grant 52205018the Fundamental Research Funds for the Central Universities,NO.NP2024302.
文摘Insects can adapt their walking patterns to complex and varied environments and retain the ability to walk even after significant changes in their physical attributes,such as amputation.Although the interleg coordination of intact insects has been widely described in previous studies,the adaptive walking patterns in free-walking insects with amputation of 1 or more legs are still unclear.The pentatomid bug Erthesina fullo exhibits a tripod gait,when walking freely on horizontal substrates,like many other insects.In this study,amputations were performed on this species to investigate changes in interleg coordination.The walking parameters were analyzed,such as the locations of touchdown and liftoff,cycle period,walking speed,and head displacement of intact and amputated insects.The results show that E.fullo displays adaptive interleg coordination in response to amputations.With 1 amputated leg,bugs changed to a 3-unit gait,whereas with 2 amputated legs they employed a wave gait.These data are helpful in exploring the motion mode control in walking insects and provide the theoretical basis for the gait control strategy of robots,when leg failure occurs.
基金financially supported by the Grant GO995/48-1 to S.N.G.from the National Priority Program SPP2416″Code-Chi-Chitin,chitosan and chitooligosaccharides and their interaction with proteins of the extracellular matrix and cellular signaling”of the German Science Foundation(DFG).
文摘Scorpions are distributed almost all over the world and inhabit rainforests,deserts,mountains,and littoral zones.Their multifunctional chelae play a key role in their biology.The chela is the pincer that has originated from the last two segments of the pedipalp.Many previous studies have focused on the morphology of the chela and the overall pincer force.The knowledge about the material properties of scorpion chelae remains rather poor.In particular,little is known about the spines located on the grasping edge of the chela.In this study,we use a combination of nanoindentation,micro-computer tomography,confocal laser scanning microscopy,scanning electron microscopy and energy-dispersive X-ray elemental analysis,to examine the mechanical properties,relative density,sclerotization level,microstructure and biomineralization of both the regular cuticle and the spine cuticle of the chela in the scorpion Androctonus bicolor.Our results show that the mechanical property values of the spine cuticle are significantly higher than those of the regular cuticle.This can reduce the risk of damage to the chela,increase the chance of indentation into the prey tissue and is very likely to result from both higher sclerotization level and biomineralization due to the accumulation of zinc.The specialized microstructure of the cuticle could contribute to the enhancement of the stiffness,strength and toughness of the chela.This study aids in better understanding the material structure,composition and properties of the scorpion chela cuticle.
基金supported by the National Natural Science Foundation of China(Nos.11932004 and HWG2022001)the Opening Fund of the State Key Laboratory of Nonlinear Mechanics,Institute of Mechanics,Chinese Academy of Sciences,China.
文摘Living organisms,such as geckos and insects,exhibit excellent climbing ability on various complex surfaces due to the hair-like hierarchical adhesive systems of their attachment devices.Over the past few decades,an increased understanding of the mechanisms of multiscale hierarchical adhesion systems and the continual improvement of theoretical modeling have promoted the rapid advancement in the design and application of biomimetic artificial adhesives.The modeling of biomimetic artificial adhesives has developed from simple structures to complex constructions with multilevel hierarchical properties.A review of advances in the development of these contact mechanics models is presented here.Adhesion and friction models considering multiscale hierarchical structural forms are discussed,with a focus on multiscale hierarchical models based on the development of the Cantor‒Borodich profiles.Finally,the most recent developments in studies of artificial setae with spatula-like ends,both axisymmetric and non-axisymmetric,are reviewed.
文摘The ability to fly is crucial for migratory insects.Consequently,the accumulation of damage on the wings over time can affect survival,especially for species that travel long distances.We examined the frequency of irreversible wing damage in the migratory butterfly Vanessa cardui to explore the effect of wing structure on wing damage frequency,as well as the mechanisms that might mitigate wing damage.An exceptionally high migration rate driven by high precipitation levels in their larval habitats in the winter of 2018–2019 provided us with an excellent opportunity to collect data on the frequency of naturally occurring wing damage associated with long-distance flights.Digital images of 135 individuals of V.cardui were collected and analyzed in Germany.The results show that the hindwings experienced a greater frequency of damage than the forewings.Moreover,forewings experienced more severe damage on the lateral margin,whereas hindwings experienced more damage on the trailing margin.The frequency of wing margin damage was higher in the painted lady butterfly than in the migrating monarch butterfly and in the butterfly Pontia occidentalis following artificially induced wing collisions.The results of this study could be used in future comparative studies of patterns of wing damage in butterflies and other insects.Additional studies are needed to clarify whether the strategies for coping with wing damage differ between migratory and nonmigratory species.
基金supported by the grants for Konstantin NADEIN from the German Research Foundation(DFG project“Functional design of beetle leg joints:morphology,tribology,and cuticular microstructure”,NA 126472-1 and DFG project“Arthropod leg joints as biological devices:design,mechanical properties and anti-friction mechanisms”,NA 1264/3-1)Stanislav N.GORB acknowledges the project support from the German Research Foundation(DFG GO 995/34-1 within the framework of the DFG SPP 2100“Soft Material Robotic Systems”).
文摘Tribological properties of femoro-tibial leg joints in two beetles,darkling beetle Zophobas morio and Congo rose chafer Pachnoda marginata were studied.Very low friction of 0.004 was revealed by the direct measurements in the joint.It is assumed that semi-solid lubricant functioning as in technical bearings is one of the leading factors of the friction minimization.Dependence of the surface texture and physical chemical properties(hydrophobicity)on the cuticle friction was analysed.Contribution of the surface texture to the tribological properties of contacting surfaces was examined by the measurement in the tribosystem“contacting surface/glass”.It is supposed that coefficient of friction(COF)decreases with decrease of surface roughness.At the same time,no statistically significant correlation was found between the hydrophobicity of the surface and the value of the friction coefficient.
基金This work was supported by the Federal Ministry of Science of Germany(BMBF)grant BioFuture 0311851 to S.Gorbby the National Natural Science Foundation of China(Grant No.90205014)863 Project 2002AA 423230 to Z.D.Dai.
文摘Geometric and micro-structure design, tribology properties of beetle joints were experimentally studied, which aimed to enlighten ideas for the joint design of MEMS.The observation by using SEM and microscopy suggested that beetle's joints consist of a concave surface matched with a convex surface. The heads of the beetles, rubbing with flat glass, were tested in fresh and dried statuses and compared with sapphire ball with flat glass. Frictional coefficient of the joint material on glass was significantly lower than that of the sapphire sphere on glass. The material of the joint cuticle for convex surface is rather stiff (the elastic modulus 4.5 Gpa) and smooth. The surface is hydrophobic (the contact angle of distilled water was 88.3° ). It is suggested here that the high stiffness of the joint material and hydrophobicity of the joint surface are parts of the mechanism minimizing friction in insect joints.
