The physiological adaptation for the "fore-mid" four-legged walking behavior of the pygmy mole cricket Xya sichuanensis

Animals have developed numerous specialized biological characteristics due to selective pressure from the environment. The pygmy mole cricket Xya sichuanensis has well-developed saltatorial hind legs for jumping and benefits for its survival, but these legs cannot be used for walking. Therefore, the typical tripedal gait used by most insects with six legs is not possible, and X. sichuanensis walks exclusively using its fore and mid legs. In this study, we describe a "fore-mid" walking pattern in X. sichuanensis. Further, we sought to deepen our understanding of the biological and physiological adaptations of this "four-legged" insect. We found the positions of tarsi points relative to the ground, integrated hind leg-abdomen structure, thickened ventral cuticle, and leg movements during walking to all show a unique biological adaptation. Of interest, X. sichuanensis was observed to demonstrate four-legged walking, underlining the general theme that insects have strong plasticity at both physiological and behavioral levels. We suggest that on an evolutionary timescale, X. sichuanensis has developed behavioral characteristics such as optimized jumping behavior and a unique walking pattern alongside specialized anatomical adaptations to enable survival in a competitive environment. This study could help explain biological and physiological adaptations for insects9 behaviors with important implications for the study of diversity in insect locomotion.