Numerical Characterization of Surface Structures of Slippery Zone in Nepenthes Alata Pitchers and its Mechanism of Reducing Locust’s Attachment

The slippery zone of inner pitchers in carnivorous plant Nepenthes alata bears highly specialized structures to serve the functions of trapping insects and restricting escape of preys. Since the surface structures of slippery zone may influence locust’s attachment, surface micromorphologies of the slippery zone were observed with scanning electron microscope (SEM) and scanning white-light interferometer (SWLI) to investigate the micromorphologies and geometrical dimensions of the surface structures. Attachment force of locust (Locusta migratoria manilensis) on the slippery zone was measured with different slanting angles, as well as measured on stainless steel plate for the purpose of comparison. The influence of slippery zone on locust attachment were analyzed based on the viewpoints of micromorphologies and geometrical dimensions of the surface structures. The slippery zone of N. alata pitchers possesses lunate cells and wax crystals with micro-nano dimensions. Measurement results presented that the attachment force of locust on slippery zones is apparently lower than that on stainless steel plates with all the corresponding slanting angles. The surface structures with appropriate geometrical dimensions and physical properties resulted in the significant decrease of attachment force by means of prohibiting locust generating effective mechanical interlock and adhesive attachment. This research probably provides a theoretical foundation for biomimeticing microstructures and function of slippery zone surface to design slippery plates for trapping disaster plague locust and other agricultural pest. Keywords: slippery zone; Nepenthes alata; locust; attachment force; surface structures