【目的】 挖掘行为是驱动金龟总科昆虫多样性演化的重要因素之一，其挖掘行为功能形态基础备受关注。然而，此前研究多局限于单一维度，缺乏将外部形态与内部肌肉结构相结合的综合分析。本研究旨在通过整合三维几何形态学与肌肉定量分析，揭示不同挖掘能力金龟子前胸结构的形态适应机制，探讨其与挖掘行为相关的功能形态演化。【方法】 以具有强、弱两种挖掘能力的8种金龟子为研究对象，利用显微CT（Micro computed tomography）扫描并三维重建其前胸背板及内部控制前足基节运动的关键肌肉（Tergal remotor, tergal promotor）。通过三维几何形态学分析前胸背板的外部形态差异，并通过测量肌肉体积、截面积及附着表面积等指标进行内部结构的定量比较。【结果】 主成分分析表明，强、弱挖掘类群的前胸背板三维形态存在显著分化。强挖掘类群的前胸背板呈现出更为陡峭的“马鞍形”隆起和流线型的“楔形”轮廓，这可能有助于分散应力和增强结构稳定性。肌肉定量分析得出，强挖掘类群中控制基节下挖的Tergal remotor肌肉在前胸背板上的附着面积比例显著高于弱挖掘类群（P<0.01），而其中段截面积、体积等指标无显著差异（P>0.05）。【结论】 金龟总科昆虫为适应挖掘行为，其前胸结构发生了协同演化，外部背板通过形态特化（如隆起和流线型轮廓）以提升力学稳定性；内部则通过增加肌肉附着面积来为发力提供更稳固的锚点和力量提升的条件，而非单纯增大肌肉体积。本研究凸显了多维定量形态学在功能形态学研究领域研究中的优势，为理解生物形态对环境的适应性进化提供了典型案例。

 [Aim]  To reveal the mechanisms underlying the morphological changes involved in the excavation behavior of scarab beetles (Scarabaeoidea), and examine how these relate to the evolution of functional morphology associated with digging behavior in this taxon. [Methods]  Eight scarab species with differing excavation abilities were selected. Micro- computer tomography (micro-CT), was used to scan and construct 3D models of the pronotum and the main internal muscles involved in forecoxal movement (the tergal remotor and tergal promotor), in these species. External differences in pronotum shape were examined using 3D geometric morphometrics, whereas internal structures were compared quantitatively by assessing their muscle volume, cross-sectional area, and attachment surface area. [Results]  Principal component analysis identified notable differences in the shape of the pronotum between strong and weak excavators. The pronotum of strong excavators has a more pronounced “saddle-shaped” arch and a more streamlined “wedge-shaped” profile, which probably aid in stress relief and increase stability. Quantitative muscle assessments revealed that the attachment area ratio of the tergal remotor muscle was significantly larger in species with stronger excavating ability (P<0.01). However, no significant differences were observed in the mid-cross-sectional area, volume, or other related measures, of this muscle (P>0.05).  [Conclusion]  Scarab beetles’ prothoracic structures reflect evolution for different levels of excavating ability. In species with strong excavating ability, the external pronotum has become more arched and streamlined to boost mechanical stability, while internally, increased muscle attachment areas create a stronger anchor and improve muscular efficiency, without overtly increasing muscle size. This study highlights the advantages of multidimensional quantitative morphology in functional morphology research, and offers a clear example of how biological structures adapt to different environmental requirements.