Fig. 1. (A) The basalar muscle (BM) of the mesothorax exposed by removal of a portion of the cuticle and underlying air sacs. The viewpoint is looking posteriorly from the rear margin of the head and slightly above the dragonfly; the base of the left forewing is visible near the upper right. White arrows show the lateral edges of the humeral plate, around which incisions were made to isolate the basalar muscle mechanically for studies of contractile performance. (B) Sample trace of wing position and velocity from a recording made using a laser distance sensor on the base of the forewing. (C) Photograph showing a dragonfly attached by its ventral thorax to a narrow glass beam (not visible) that extends from a strain gauge. A fine-gauge thermocouple and EMG electrodes are inserted into the thorax. The laser distance sensor is shown at the upper right. We have drawn a red line to depict the laser beam striking a white spot painted at the base of the right forewing. (D) Diagram showing the geometry of the basalar muscle attachment to the base of the forewing, an approximation of the EMG recording electrodes (these are differential electrodes referenced to a third electrode in the abdomen that is not shown) and the method used to calculate wing position from the laser distance sensor.
