Meeting Abstract
Recent research suggests that abdominal actuation during insect flight may contribute to control and stability via inertial redirection of flight forces. All hymenoptera within the suborder Apocrita have a highly constricted segment of the abdomen called the petiole. This derived character can occupy up to 30-40% of the total body length and provide key insight into the possible dual roles of the abdomen as both an actuator and sensor for flight control. We used mud daubers (Sceliphron caementarium) as model organisms to ask if this structure has morphologies that are consistent with roles in both and sensing and flight control. We develop an Euler-Lagrange multibody dynamics model to predict flight responses to perturbations that arise from either external forces or internal muscle torques. Mechanical parameters for the model including the damping, mass, and spring constants of the abdominal segments were measured from tethered individuals subject to impulse and point load tests. The abdominal/petiole unit behaves as a damped mass system. Our multibody dynamics model also shows that the trajectory of the animal is sensitive to the geometry, position, and mechanics of the petiole and position of the abdomen. Thus changes in abdominal position with respect to the head/thorax position yields significant changes in the animal’s trajectory (between a 1 cm rise and a 5 cm fall). Additionally, scanning electron microscopy (SEM) on preserved specimens reveals the existence of sensory hair plates at the base of peduncle-petiole joint, reminiscent of Böhm’s bristles in antennal sensory systems. Moreover, the presence of sensory hair plates suggests that such small angular changes can be detected by the nervous system. Thus the dual roles of the abdomen are supported by our observations.
