Biomechanical adaptations enable phoretic mite species to occupy distinct spatial niches on host burying beetles.

Niche theory predicts that ecologically similar species coexist by minimizing interspecific competition through niche partitioning. Therefore, understanding the mechanisms of niche partitioning is essential for predicting interactions and coexistence between competing organisms. Here, we study two phoretic mite species, and that coexist on the same host burying beetle and use it to 'hitchhike' between reproductive sites.

Bumblebees negotiate a trade-off between nectar quality and floral biomechanics.

How and why pollinators choose which flowers to visit are fundamental, multifaceted questions in pollination biology, yet most studies of floral traits measure simple relative preferences. Here, we used vertically and horizontally oriented slippery-surfaced artificial flowers to test whether bumblebees could make a trade-off between floral handling difficulty and nectar sucrose concentration. We quantified foraging energetics, thereby resolving the rationale behind the bees' foraging decisions.

Extreme suction attachment performance from specialised insects living in mountain streams (Diptera: Blephariceridae).

Suction is widely used by animals for strong controllable underwater adhesion but is less well understood than adhesion of terrestrial climbing animals. Here we investigate the attachment of aquatic insect larvae (Blephariceridae), which cling to rocks in torrential streams using the only known muscle-actuated suction organs in insects. We measured their attachment forces on well-defined rough substrates and found that their adhesion was less reduced by micro-roughness than that of terrestrial climbing insects.

Developmental Nutrition Affects the Structural Integrity of a Sexually Selected Weapon.

Males in many species engage in physical combat over access to mates, and sexual selection has led to the evolution of weapons to enhance contest performance. The size of these often-elaborate structures is known to be exquisitely sensitive to nutrition. However, we know very little about the degree to which nutrition affects other attributes of animal weapons that can be crucial to fighting.

How a sticky fluid facilitates prey retention in a carnivorous pitcher plant (Nepenthes rafflesiana).

Nepenthes pitcher plants grow in nutrient-poor soils and produce large pitfall traps to obtain additional nutrients from animal prey. Previous research has shown that the digestive secretion in N. rafflesiana is a sticky viscoelastic fluid that retains insects much more effectively than water, even after significant dilution.

Role of legs and foot adhesion in salticid spiders jumping from smooth surfaces.

Many spiders and insects can perform rapid jumps from smooth plant surfaces. Here, we investigate how jumping spiders (Pseudeuophrys lanigera and Sitticus pubescens) avoid slipping when accelerating. Both species differed in the relative contribution of leg pairs to the jump.

Disentangling the role of surface topography and intrinsic wettability in the prey capture mechanism of Nepenthes pitcher plants.

Nepenthes pitcher plants capture prey with leaves specialised as pitfall traps. Insects are trapped when they 'aquaplane' on the pitcher rim (peristome), a surface structured with macroscopic and microscopic radial ridges. What is the functional significance of this hierarchical surface topography? Here, we use insect pad friction measurements, photolithography, wetting experiments and physical modelling to demonstrate that the ridges enhance the trap's efficacy by satisfying two functional demands on prey capture: Macroscopic ridges restrict lateral but enhance radial spreading of water, thereby creating continuous slippery tracks which facilitate prey capture when little water is present.

The mechanics of nectar offloading in the bumblebee and implications for optimal concentrations during nectar foraging.

Nectar is a common reward provided by plants for pollinators. More concentrated nectar is more rewarding, but also more viscous, and hence more time-consuming to drink. Consequently, theory predicts an optimum concentration for maximizing energy uptake rate, dependent on the mechanics of feeding.

Shear-sensitive adhesion enables size-independent adhesive performance in stick insects.

The ability to climb with adhesive pads conveys significant advantages and is widespread in the animal kingdom. The physics of adhesion predict that attachment is more challenging for large animals, whereas detachment is harder for small animals, due to the difference in surface-to-volume ratios. Here, we use stick insects to show that this problem is solved at both ends of the scale by linking adhesion to the applied shear force.

Dynamic biological adhesion: mechanisms for controlling attachment during locomotion.

The rapid control of surface attachment is a key feature of natural adhesive systems used for locomotion, and a property highly desirable for man-made adhesives. Here, we describe the challenges of adhesion control and the timescales involved across diverse biological attachment systems and different adhesive mechanisms. The most widespread control principle for dynamic surface attachment in climbing animals is that adhesion is 'shear-sensitive' (directional): pulling adhesive pads towards the body results in strong attachment, whereas pushing them away from it leads to easy detachment, providing a rapid mechanical 'switch'.

Venus flytrap trigger hairs are micronewton mechano-sensors that can detect small insect prey.

Venus flytraps detect moving insects via highly sensitive, action potential (AP)-producing trigger hairs, which act as high-sensitivity levers, crucial for prey capture and digestion. Controlled stimulation revealed that they can trigger APs for deflections >2.9°, angular velocities >3.

Strong Wet and Dry Adhesion by Cupped Microstructures.

Recent advances in bio-inspired microfibrillar adhesives have resulted in technologies that allow reliable attachment to a variety of surfaces. Because capillary and van der Waals forces are considerably weakened underwater, fibrillar adhesives are however far less effective in wet environments. Although various strategies have been proposed to achieve strong reversible underwater adhesion, strong adhesives that work both in air and underwater without additional surface treatments have yet to be developed.

Froghoppers jump from smooth plant surfaces by piercing them with sharp spines.

Attachment mechanisms used by climbing animals facilitate their interactions with complex 3D environments and have inspired novel types of synthetic adhesives. Here we investigate one of the most dynamic forms of attachment, used by jumping insects living on plants. Froghopper insects can perform explosive jumps with some of the highest accelerations known among animals.

Scaling of claw sharpness: mechanical constraints reduce attachment performance in larger insects.

Claws are the most widespread attachment devices in animals, but comparatively little is known about the mechanics of claw attachment. A key morphological parameter in determining attachment ability is claw sharpness; however, there is a conflict between sharpness and fracture resistance. Sharper claws can interlock on more surfaces but are more likely to break.

Coping with the climate: cuticular hydrocarbon acclimation of ants under constant and fluctuating conditions.

Terrestrial arthropods achieve waterproofing by a layer of cuticular hydrocarbons (CHCs). At the same time, CHCs also serve as communication signals. To maintain waterproofing under different climate conditions, insects adjust the chemical composition of their CHC layer, but this may affect the communication via CHCs.

Jumping without slipping: leafhoppers (Hemiptera: Cicadellidae) possess special tarsal structures for jumping from smooth surfaces.

Many hemipteran bugs can jump explosively from plant substrates, which can be very smooth. We therefore analysed the jumping performance of froghoppers ( Aphrophoridae) and leafhoppers ( Cicadellidae) taking off from smooth (glass) and rough (sandpaper, 30 µm asperity size) surfaces. On glass, the propulsive hind legs of froghoppers slipped, resulting in uncontrolled jumps with a fast forward spin, a steeper angle and only a quarter of the velocity compared with jumps from rough surfaces.

Biomechanics of shear-sensitive adhesion in climbing animals: peeling, pre-tension and sliding-induced changes in interface strength.

Many arthropods and small vertebrates use adhesive pads for climbing. These biological adhesives have to meet conflicting demands: attachment must be strong and reliable, yet detachment should be fast and effortless. Climbing animals can rapidly and reversibly control their pads' adhesive strength by shear forces, but the mechanisms underlying this coupling have remained unclear.

Elasto-capillarity in insect fibrillar adhesion.

The manipulation of microscopic objects is challenging because of high adhesion forces, which render macroscopic gripping strategies unsuitable. Adhesive footpads of climbing insects could reveal principles relevant for micro-grippers, as they are able to attach and detach rapidly during locomotion. However, the underlying mechanisms are still not fully understood.

Extreme positive allometry of animal adhesive pads and the size limits of adhesion-based climbing.

Organismal functions are size-dependent whenever body surfaces supply body volumes. Larger organisms can develop strongly folded internal surfaces for enhanced diffusion, but in many cases areas cannot be folded so that their enlargement is constrained by anatomy, presenting a problem for larger animals. Here, we study the allometry of adhesive pad area in 225 climbing animal species, covering more than seven orders of magnitude in weight.

Functional morphology and efficiency of the antenna cleaner in Camponotus rufifemur ants.

Contamination of body surfaces can negatively affect many physiological functions. Insects have evolved different adaptations for removing contamination, including surfaces that allow passive self-cleaning and structures for active cleaning. Here, we study the function of the antenna cleaner in Camponotus rufifemur ants, a clamp-like structure consisting of a notch on the basitarsus facing a spur on the tibia, both bearing cuticular 'combs' and 'brushes'.

On Heels and Toes: How Ants Climb with Adhesive Pads and Tarsal Friction Hair Arrays.

Ants are able to climb effortlessly on vertical and inverted smooth surfaces. When climbing, their feet touch the substrate not only with their pretarsal adhesive pads but also with dense arrays of fine hairs on the ventral side of the 3rd and 4th tarsal segments. To understand what role these different attachment structures play during locomotion, we analysed leg kinematics and recorded single-leg ground reaction forces in Weaver ants (Oecophylla smaragdina) climbing vertically on a smooth glass substrate.

Rate-dependence of 'wet' biological adhesives and the function of the pad secretion in insects.

Many insects use soft adhesive footpads for climbing. The surface contact of these organs is mediated by small volumes of a liquid secretion, which forms thin films in the contact zone. Here, we investigate the role of viscous dissipation by this secretion and the 'bulk' pad cuticle by quantifying the rate-dependence of the adhesive force of individual pads.

Effect of shear forces and ageing on the compliance of adhesive pads in adult cockroaches.

The flexibility of insect adhesive pads is crucial for their ability to attach on rough surfaces. Here, we used transparent substrates with micropillars to test in adult cockroaches (Nauphoeta cinerea) whether and how the stiffness of smooth adhesive pads changes when shear forces are applied, and whether the insect's age has any influence. We found that during pulls towards the body, the pad's ability to conform to the surface microstructures was improved in comparison to a contact without shear, suggesting that shear forces make the pad more compliant.

Mechanotransduction: use the force(s).

Mechanotransduction - how cells sense physical forces and translate them into biochemical and biological responses - is a vibrant and rapidly-progressing field, and is important for a broad range of biological phenomena. This forum explores the role of mechanotransduction in a variety of cellular activities and highlights intriguing questions that deserve further attention.

How to catch more prey with less effective traps: explaining the evolution of temporarily inactive traps in carnivorous pitcher plants.

Carnivorous Nepenthes pitcher plants capture arthropods with specialized slippery surfaces. The key trapping surface, the pitcher rim (peristome), is highly slippery when wetted by rain, nectar or condensation, but not when dry. As natural selection should favour adaptations that maximize prey intake, the evolution of temporarily inactive traps seems paradoxical.