Beetle exoskeletal structure and surfaces determine specialized functions: Two case studies

The exoskeletal cuticles of insects are made of materials that could have a wide range of material properties, leading to numerous structures and surfaces with selective advantages. Some of them are functional specifically for interacting with other biological structures or the environment. This thesis presents two hybrid experimental/theoretical investigations of how the exoskeletal structure and surface of beetles help mediate their interaction with other objects, to achieve certain functions that make them advantageous in their habitats. The first study investigates the morphology, stiffness and stress distribution in the click-beetle peghold, which works in connection with the mesosternal lip to maintain the beetle body in brace position, while elastic energy is being stored in other body parts. The work confirms that the unique morphology of the peghold results in a stiff and robust structure that is able to withstand significant energy storage without material failure while maintaining the body in brace position. The peghold is the key exoskeletal structure for the beetle to achieve explosive “jump” that have liberating and self-righting functions. The second study investigates the tribological and wettability properties of diffraction gratings present on the outer surfaces of various iridescent ground beetle species, in comparison to their counterparts without diffraction gratings. The diffraction gratings on ground beetles are hypothesized to modify frictional performance and degree of wettability, that helps mediate the beetles’ interaction with fibrous and soil surfaces in environment. From the scanning electron microscopy, goniometry and tribological studies, iridescent species within the Scarabaeidae family have both significantly modified friction coefficient against fibrous surface and contact angles. The degree of wettability also has an effect on adhesion force onto wet surfaces. Thus, these two case studies show explicit functions of the body structures and surface structures of beetles.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Mechanical Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2019

Author dc:creator

• Wei, Lihua

Contributors dc:contributor

• Dunn, Alison C

• Exoskeletal structures
• Insect tribology

Statement dc:rights

• Copyright 2019 Lihua Wei

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/105949

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/105949