Meeting Abstract
The halteres of flies are reduced hindwings that provide mechanosensory information during flight. Although these organs are crucial for flight , their role in other behaviors is not understood. Because afferent neurons are known to be sensitive to a wide range of motions, the information transduced by halteres is dependent on motion. We observed haltere movements of 20 fly families. By capturing high-speed video of halteres during tethered flight and during free walking, we discovered that all flies oscillate their halteres during flight, but only certain families of flies oscillate their halteres during walking. The oscillations seen in these flies were highly dependent on phylogeny. Some flies of the suborder Nematocera showed uncoordinated oscillations while walking and standing. Many more recently evolved families of flies do not move their halteres at all unless flying. However, two of the most recently evolved groups show characteristic patterns of oscillations. All families of flies in the Calyptratae oscillated their halteres during walking, and did so at their wingbeat frequency. Flies in the superfamily Tephritoidea moved their halteres with slow, irregular patterns, and did so during both walking and standing. Furthermore, we found that flies often moved their halteres independently, varying the phase of oscillation of one haltere relative to the other. This observation is in contrast to haltere movements in flight, in which case they are strictly in phase with each other. These observations suggest that in many flies, the halteres may be multi-functional and could provide different types of information depending on behavioral context. Our explicitly comparative and evolutionary approach has revealed previously undescribed diversity in haltere movements, and possibly new functional roles for the haltere in fly behavior.
