Excavation mechanics of the elongated female rostrum of the acorn weevil Curculio glandium (Coleoptera; Curculionidae)

Abstract

Elongated rostra (snouts) are remarkable features of many female weevils. The female of Curculio glandium uses the snout to excavate channels in acorns to oviposit. Considering the slenderness of the rostrum, the excavation of channels in solid substrates without buckling is a challenging task from both engineering and biological points of view. Here we aimed to examine the roles of the material properties and morphology of the rostrum in its buckling resistance. We employed microscopy techniques, non-destructive material characterisation and finite element (FE) modelling to shed more light on the excavation mechanics of the rostrum. We found that sexual dimorphisms are present not only in the length but also in the material, particularly the elastic modulus, and morphological features, particularly the curvature and thickness of the cuticular layers. Our FE modelling showed that those factors play essential roles to maximise the buckling resistance and minimise the bending resistance of the female rostrum. Considering that during excavation, the rostrum needs to be straightened without buckling, the functionality of the rostrum is likely to be a compromise between the flexibility and stiffness.

Material gradients in gastropod radulae and their biomechanical significance: a combined approach on the paludomid Lavigeria grandis

“…Garcia-Castineiras et al 1978 ; Fujimori 1978 ; Gast and Lee 1978 ; Giurginca et al 2015 ). This protocol (Michels and Gorb 2012 ) was applied and enabled to find functional significances of material properties in many studies on arthropod endocuticle (Wang et al 2019 ), wings (Rajabi et al 2018 ; Ma et al 2022 ), foot attachment devices and legs (Peisker et al 2013 ; Rebora et al 2018 ; Petersen et al 2018 ; Friedrich and Kubiak 2018 ; Jandausch et al 2018 ; Beutel et al 2020 ; Büsse et al 2021 ; Li et al 2021 ; Büscher et al 2021 ), thorax structure (Casey et al 2022 ), antennae (Saltin et al 2019 ), mouthparts (Michels et al 2012 ; Michels and Gorb 2015 ; Büsse and Gorb 2018 ; Weihmann and Wipfler 2019 ; Matsumura et al 2021a , b ; Lehnert et al 2021 ; Sun et al 2021 ; Wei et al 2022 ) or genitals (Matsumura et al 2014 , 2017 , 2020a , b , 2021a , b ; Kamimura et al 2021 ). In addition, this protocol was cross-validated by employing AFM-Nanoindentation at least for hair of foot attachment devices in a lady beetle (Peisker et al 2013 ).…”

Double-spiral: a bioinspired pre-programmable compliant joint with multiple degrees of freedom

“…In contrast, many functional spirals in animal and plant structures experience high deformations through coiling and uncoiling. The intromittent organs of beetles [25], proboscis of Lepidoptera [26], rostra of weevils [27], tentacles of octopuses [28], chameleon tail [29], fern fronds [30,31] and millipede body [32] are only a few examples of highly extensible biological spirals. Our aim here is to use spiral-inspired strategies to design and manufacture mechanical elements with high extensibility.…”