MYHRVOLD, C.*; SANE, S.; DANIEL, T.; Univ. of Washington, Seattle; Univ. of Washington, Seattle; Univ. of Washington, Seattle: The flexible halteres of the cranefly Holorusia rubiginosa

Animal locomotion requires navigation. As such, animals have evolved a variety of navigational devices, which often take the form of inertial sensors. Because they move in three dimensions, flying insects have greater navigational problems than terrestrial animals. Halteres, shown in past studies of Calliphora to be inertial sensors, are an example of an inertial sensor that flying insects have evolved to cope with their navigational problems. Unlike the short, stubby halteres of Calliphora, crane flies such as Holorusia Rubiginosa have elongated halteres with knob-like tips. Does the unique structure and mechanics of crane fly halteres affect the way in which they function? We performed several experiments to determine the function of crane fly halteres. These included ablating the halteres, close-up, high-speed video of a tethered fly�s halteres, and finite element modeling. Crane fly halteres are visible with the naked eye; this let us do free-flight experiments in a flight chamber. We tested crane flies with and without halteres, and in some cases reattached the halteres to see if any flight would be regained. The free-flight experiments showed that crane flies can initiate, but not sustain, flight without halteres. Another set of experiments examined tethered crane flies with high-speed videography. We digitized points on each haltere to determine if bending occurred when the halteres reached the top and bottom of each stroke. The experiment showed that a significant amount of bending did occur. We also found that the halteres oscillate independent of the wings. Finite element modeling showed that, by changing the elasticity of the halteres, we could �tune� them to encode specific forces. Taken together, our results indicate that crane fly halteres may be flexible, tunable gyroscopes.