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Fig. 48. Posterior view of stridulation movement made while male turns 
around in cage, pressing the wing-tips against the glass (insert). X and Y 
coordinates of the medial points of the f.emoro-tibial joints were measured 
instead of angles w r hich could not be discerned readily. Angle of view is 
about 10° from the horizontal. Y-coordinates (+ triangle) approaching unity 
cr overlapping represent parallel motion in the plane of the stroke, X-co- 
ordinates approaching unity or overlapping represent convergent motion 
at right angles to the plane of rotation, i.e., toward the midline. Note that 
the greatest Y-separation of the two femoral tips coincides with convergence 
in the X-dimension, i. e., the femoral tips overlap the midline and must 
displace one another if any pressure is to be placed on the tegminal file, 
imposing the asynchrony of downward motion observed in Figs. 44-47. 
