Characterization of material properties of bed bug cuticle (Cimex lectularius)

As a result of the plant-herbivore coevolutionary arms race, plants have evolved a variety of physical and chemical defenses against insects and other herbivores.  Nonglandular trichomes are microscopic plant hairs that provide an important and effective physical defense against some insects.  By coincidence, trichomes on leaves from bean plants (Phaseolus vulgaris)  have been shown to pierce and entrap bed bugs (Cimex lectularius), although bed bugs and bean plants do not share any evolutionary association.  In recent years, bed bugs have reemerged globally as a major pest.  Therefore there is general interest in the development of control methods, particularly environmentally-benign physical methods that do not involve insecticides.  In order to understand the requirements of a biomimetic physical control method based on the piercing trichomes, the mechanical properties of bed bug cuticle have been characterized using nanoindentation.  Nanoindentation was performed on the underside of bed bug tarsi (distal segments on the legs), including the pretarsal claw area.  Only specific locations have been documented to be pierced.  These locations were chosen for nanoindentation in addition to adjacent non-pierced areas, in order to identify the causes of mechanical vulnerability.  Some areas of the pretarsal claws were easier to pierce (required a lower force) than the cuticle of the tarsal subsegments, and required a smaller displacement of the probe before piercing occurred.