Fight, Retreat, Repeat: Field observation of male-male agonistic behavior in the wood-feeding cockroach, Panesthia angustipennis spadica (Dictyoptera: Blattodea: Blaberidae)

Conflict is one of the most critical factors affecting the behavior of animals related to their reproduction and survival, with aggressive interactions being central to acquiring resources or mating partners. This phenomenon is more common among males than females, impacting reproduction strategy and beginning of biparental care. Investigating such interactions in species closely related to social species can be illuminating, offering valuable insights into the factors that influence the emergence and maintenance of more complex social behaviors. In this context, we present a field study of male-male agonistic behavior in the wood-feeding cockroach, Panesthia angustipennis. Panesthia is the closest genus to the subsocial genus Salganea, which is known for its biparental care. Our field observations reveal a characteristic behavior where one male pushes a rival away from a female. The victorious male repeatedly returns to a specific site near the female, suggesting a strategy to minimize unnecessary conflict or protect the female. This behavior provides insights into the potential evolutionary strategies that may have evolved in the common ancestor shared by Salganea and Panesthia. Notably, the displaced males persistently reengage, highlighting the high resource value attributed to females and the consequential intensity of male competition. This study not only sheds light on the aggressive and pacifist tendencies in P. angustipennis but also contributes to understanding the evolutionary development of social structures in Salganea. Further experimental investigations into the aggressive behaviors of P. angustipennis will enhance our comprehension of the factors shaping the evolution of sociality in these species.