Meeting Abstract

P2-110   -   The flying insect thoracic cuticle is heterogenous in structure and in thickness-dependent modulus gradation Casey, C*; Yager, C; Jankauski, M; Heveran, C; Montana State University; Montana State University; Montana State University; Montana State University cailin.casey@student.montana.edu

The thorax is a specialized thin-walled cuticular structure central to insect flight. The structure, composition, and material properties of the thorax may influence its dynamic behavior in-vivo. However, the thorax cuticle material properties, and how these properties vary across anatomical regions of the thorax and between insect taxa, are not known. We investigated the microscale structure, composition, and modulus of the thorax cuticle through histology, confocal laser scanning microscopy, and nanoindentation. We determined that thorax cuticle properties are highly dependent on anatomical region and species. The mean thorax cuticle thickness did not differ between fliers with asynchronous (honey bee; Apis mellifera, 7.11 ± 1.47 GPa) and synchronous (hawkmoth; Manduca sexta, 6.75 ± 1.92 GPa) muscles. However, modulus gradation differed for these species. In some regions, A. mellifera had a positive linear modulus gradient from cuticle interior to exterior of about 2 GPa. In M. sexta, modulus gradients through cuticle thickness varied and were not well represented by linear fits. Through finite element modeling, we assessed how modulus cuticle gradients influenced maximum stress. We found that cuticle with linearly graded modulus generally experienced lower peak stresses than cuticle with homogenous modulus. High-resolution multi-faceted materials assessment highlights the variation in microscale cuticle properties and points to factors that may (modulus gradation) and may not (average modulus) contribute to different flight forms. This work advances our understanding of thorax cuticle structural and material heterogeneity and the potential benefits of material gradation to insect flight.