Attachment performance of stick insects (Phasmatodea) on convex substrates.

Area of Science:

• Biomechanics
• Insect locomotion
• Adhesive strategies

Background:

• Phasmatodea (stick and leaf insects) exhibit remarkable camouflage and plant substrate adaptation.
• Research on stick insect attachment has primarily focused on flat surfaces, neglecting natural curved substrates.
• Understanding attachment on curved surfaces is crucial for phytophagous insects.

Purpose of the Study:

• To investigate the influence of substrate curvature on the attachment performance of two stick insect species.
• To quantify attachment forces (traction and pull-off) on curved surfaces of varying diameters.
• To analyze the role of tarsal morphology and usage in attachment on curved substrates.

Main Methods:

• Mechanical traction and pull-off force measurements on curved substrates with varying diameters.
• Analysis of tarsal usage, including number of tarsi/tarsomeres in contact, and leg/body posture.
• Comparison of attachment performance between two stick insect species with different tarsal lengths.

Main Results:

• Substrate curvature significantly impacts stick insect attachment ability.
• Traction force decreases, while pull-off force increases with increasing substrate curvature.
• Shorter tarsi showed reduced forces, particularly on thinner substrates (diameters smaller than tarsal length).
• Attachment forces are influenced by contact area, leg/body orientation, and tibiotarsal angle.

Conclusions:

• Stick insect attachment is highly sensitive to substrate curvature, a dominant factor in their natural environment.
• Tarsal length plays a role in attachment on smaller diameter substrates.
• The findings provide crucial quantitative data on insect attachment mechanics on naturalistic, curved surfaces.