Individual evaluation of attachment strength at each adhered point in the silk foothold constructed by bagworms for walking and dangling

Silk use in survival strategies among silk-producing arthropods is versatile and ingenious. Bagworms employ silk for a variety of functions, including nest construction, anchoring, and dangling. We recently discovered a novel use of silk for locomotion. Bagworms create a ladder-like foothold, allowing them to walk without prolegs, by spinning a silk thread in a zigzag pattern and controlling the adhesive discharge to secure the folded parts to the substrate. While the bagworm silk thread's strength and toughness are known to be sufficient for supporting their weight during walking and dangling, the attachment strength of the foothold's glued parts has not been assessed. In this study, we evaluate the attachment strength of each glued part and unveil an energy-efficient design of the foothold that ensures safe walking and dangling. This safety design for bagworm locomotion could inspire novel designs for locomotion systems in soft robotics.