THE CONTROL OF WING KINEMATICS BY 2 STEERING MUSCLES OF THE BLOWFLY (CALLIPHORA-VICINA)

We used a combination of high speed video and electrophysiological rec ordings to investigate the relationship between wing kinematics and th e firing patterns of the first (b1) and second (b2) basalar muscles of tethered Eying blowflies (Calliphora vicina). The b1 typically fires once during every wing stroke near the time of the dorsal stroke rever sal. The b2 fires either intermittently or in bursts that may be elici ted by a visual turning stimulus. Sustained activation of the b1 at ra tes near wing beat frequency appears necessary for the tonic maintenan ce of stroke amplitude. In addition, advances in the phase of b1 activ ation were correlated with both increased wing protraction during the down-stroke and increased stroke amplitude. Similar kinematic alterati ons were correlated with b2 spikes, and consequently, both muscles may function in the control of turns toward the contralateral side. The e ffects of the two muscles were evident within a single stroke period a nd decayed quickly. Kinematic changes correlated with b1 phase shifts were graded, suggesting a role in compensatory course stabilization. I n contrast, b2 spikes were correlated with all-or-none changes in the wing stroke, a characteristic consistent with a role in mediating rapi d turns towards or away from objects.