INTRODUCTION: Firebugs (Pyrrhocoris apterus), common hemipteran insects, remain physically connected in post-copulatory tandems for periods ranging from two hours to seven days, a behavior thought to function as mate guarding. During this time, pairs actively navigate their environment and respond to external stimuli, including rapidly disengaging when threatened.

AIM(S): The dynamics and functional consequences of this behavior are largely understudied. Tandem locomotion in firebugs provides a natural system for studying distributed sensorimotor control and coordination between physically coupled individuals. The aim of this study was to quantify the kinematics of tandem movement and determine whether locomotor leadership is biased toward one sex and/or influenced by body size.

METHOD(S): Connected pairs collected in the wild (N=41) and raised in controlled conditions (N=10) were recorded for 15 minutes in a circular arena. Video recordings were analyzed using a DeepLabCut-based pose estimation model. Locomotor parameters including speed, traveled distance, trajectory, and angles between body parts were extracted and analyzed.

RESULTS: Preliminary analyses indicate strong female-biased leadership during tandem locomotion, with females contributing most of the traveled distance and directional changes. The influence of body size remains inconclusive, as females are generally larger than males, limiting independent assessment of size effects.

CONCLUSIONS: These findings suggest that tandem locomotion in firebugs is characterized by asymmetric movement control, potentially reflecting evolutionary trade-offs and biomechanical limitations. Ongoing analyses of leg kinematics, antennal movement, and behavioral unsupervised clustering will further clarify coordination strategies and behavioral states during prolonged post-copulatory association.

FINANCIAL SUPPORT: Self-funded