Mechanical damping affects the rapid return of cricket antennae

Filiform antennae are common among insects, such as the house cricket (Acheta domesticus). These antennae are used as mechanosensory structures which bend readily in response to contact with objects in their environment. Once bent or deflected, the antennae will reposition to their resting position. We analyzed the recovery of antennae deflecting at four distances along the flagellum. Measurements were made on restrained live crickets, with the head and joints associated with the scape and pedicel held rigid with epoxy, allowing only the flagellum to bend around a fixed obstacle. We determined 1) the antennae returned quickly to their initial positions after being perturbed in either ventral or dorsal directions with a time constant for an exponential decay of 1/e = 40 ms and 2) antennae rarely oscillated while returning from the deflection, with the tendency to oscillate decreasing with a more distal deflection. The lack of oscillations provide evidence the antennae are damped. There is a trade-off between speed and oscillations depending on the level of damping. The right magnitude of damping can suppress the vibrations (mechanical noise) without excessively slowing the movements of the antennae. This would allow the antenna to be quickly prepared for new tactile input which would be advantageous to the cricket.