Postembryonic development of the predatory strike mechanics in a praying mantis (Insecta: Mantodea)

Abstract One of the best‐known examples of prey‐capturing devices in insects is the predatory forelegs of praying mantises. Their efficiency depends on both kinematic (structure and metrics of leg segments) and kinetic (muscular propulsion) parameters. Both aspects are subject to specific size‐scaling relationships. Throughout their postembryonic development, mantises undergo a drastic increase in size while retaining a comparably consistent appearance. Size‐related sexual dimorphism may cause similar effects on the prey‐capturing dynamics between the sexes. Due to the different scaling relationships between linear (segment lengths), area (muscle cross‐section) and cubic (body volume or mass) parameters, compensatory changes in either morphology or behaviour are expected to occur. We investigated the changes of the predatory strike in the mantis Hierodula majuscula throughout its postembryonic development and in light of sexual dimorphism in this species, using high‐speed videography and striking force measurements. We measured the impact force of the forelegs of different stages and the strike durations, joint angle changes and velocities during the movement sequences of their strikes. We show that striking forces grow hyperallometrically (to the power of 0.81) with the body weight across the stages. An increasing force was associated with an increase in the tangential velocity of the tibia. In larger animals, the duration of the sweeping phase of the strike increases with the decrease in angular velocities of the leg joints. Interestingly, the striking forces changed differently across stages and sexes over consecutive days without catching success, with increasing force in all animals except for adult males, indicating varying nutritional demands in the respective groups. These results elucidate the relationship between growth physiology and the corresponding kinematic and kinetic implications during the development of this hemimetabolous predator.