Structural design and biomechanics of friction-based releasable attachment devices in insects

Design of attachment devices in insects varies enormously inrelation to different functional loads. Many systems, locatedon different parts of the body, involve surfaces with particularfrictional properties. Such systems evolved to attach partsof the body to each other, or to attach an insect to the substratumby providing fast and reversible attachment/detachment. Amongthese systems, there are some that deal with predefined surfaces,and others, in which one surface remains unpredictable. Thefirst type of system occurs, for example, in wing-locking devicesand head-arresting systems and is called probabilistic fasteners.The second type is mainly represented by insect attachment padsof two alternative designs: hairy and smooth. The relationshipbetween surface patterns and/or mechanical properties of materialsof contact pairs results in two main working principles of thefrictional devices: mechanical interlocking, or maximizationof the contact area. We give an overview of the functional designof two main groups of friction-based attachment devices in insects:probabilistic fasteners and attachment pads.