Attachment Performance of Stick Insects (Phasmatodea) on Plant Leaves with Different Surface Characteristics

Abstract

Herbivorous insects and plants exemplify a longstanding antagonistic coevolution, resulting in the development of a variety of adaptations on both sides. Some plant surfaces evolved features that negatively influence the performance of the attachment systems of insects, which adapted accordingly as a response. Stick insects (Phasmatodea) have a well-adapted attachment system with paired claws, pretarsal arolium and tarsal euplantulae. We measured the attachment ability of Medauroidea extradentata with smooth surface on the euplantulae and Sungaya inexpectata with nubby microstructures of the euplantulae on different plant substrates, and their pull-off and traction forces were determined. These species represent the two most common euplantulae microstructures, which are also the main difference between their respective attachment systems. The measurements were performed on selected plant leaves with different properties (smooth, trichome-covered, hydrophilic and covered with crystalline waxes) representing different types among the high diversity of plant surfaces. Wax-crystal-covered substrates with fine roughness revealed the lowest, whereas strongly structured substrates showed the highest attachment ability of the Phasmatodea species studied. Removal of the claws caused lower attachment due to loss of mechanical interlocking. Interestingly, the two species showed significant differences without claws on wax-crystal-covered leaves, where the individuals with nubby euplantulae revealed stronger attachment. Long-lasting effects of the leaves on the attachment ability were briefly investigated, but not confirmed.

Attachment performance of the ectoparasitic seal louse Echinophthirius horridus

“…While non-parasitic insects showed maximum safety factors around 350 (Formicidae; Atta cephalotes) 64 , the avian ectoparasite C. pallida and the bee ectoparasite B. coeca generated safety factors of around 1000-3000 28,54 . Thereby, the first five presented insect species use their claws as single-tipinterlocking systems for attachment to the substrate 62,64,69,70 , where the claw tip interacts with surface asperities. Crataerina pallida relies on a tridentate claw system that clamps into the fibrous substrate 54 and B. coeca even uses a comb-like structure to properly attach to the bee hair by clamping a relatively higher number of fibrous elements with the multiple claw tips 28 (schematically shown on the x-axis of Fig.…”

Self‐Organized Stick Insect‐Like Locomotion under Decentralized Adaptive Neural Control: From Biological Investigation to Robot Simulation

“…The walking dynamics of insects might be influenced by the substrates on which the animals locomote. In stick insects, [ 18,81,82 ] the quality of the substrate influences the forces the animals produce to stay attached to it. This can correlate with the forces the insects are able to exert on the substrates for locomotion, such as the generation of propulsion.…”

Leaves that walk and eggs that stick: comparative functional morphology and evolution of the adhesive system of leaf insect eggs (Phasmatodea: Phylliidae)

“…Observations obtained from captive breeding suggest that the eggs require a sufficiently high ambient humidity to complete embryonic development and hatch [ 24 , 25 ]. The different strategies for surface adaptation and the presence of different glue compositions (see below) potentially allow the eggs to bind to specific surfaces of certain food plants, which are characterised by their surface structure or chemistry [ 57 ]. Yet, the eggs of several species lack such adhesive mechanisms, but instead possess structures that we hypothesise to absorb and store water (e.g.…”