Biologically-constrained insect models enable realistic simulations and improve biomechanical predictions of locomotion

Animal locomotion emerges from the complex interplay of morphology, neural control, and biomechanics, involving both active and passive elements. Insect have attracted much interest, and a rich ecosystem of computational models exists for insect locomotion. However, while active control mechanisms have been extensively studied, obtaining accurate and useful models remains challenging due to limited understanding of how detailed anatomical constraints and passive biomechanical properties shape movement. To address this, we developed anatomically accurate 3D models of the adult desert locust and mole cricket, two orthopteran insects that share a basic body plan but exhibit strikingly different morphologies linked to their habitats and specialized locomotor behaviors -- jumping in locusts versus subterranean digging in mole crickets. We fine-tuned these models using precise morphometric measurements for each major body segment. Furthermore, we quantified passive joint dynamics through high-speed videography of anesthetized locust, revealing a two-phase return motion and history-dependent resting angles. By integrating these biologically grounded constraints into physical simulations, we significantly narrowed the parameter space, resulting in more realistic simulations. Our approach provides new tools for predicting biologically relevant, yet experimentally challenging variables, such as joint torques and contact forces, which contribute directly to the understanding of the underlying biological phenomena. Moreover, these improved simulations offer valuable insight for designing energy-efficient soft robotic systems.