Fig. 4. Cost per contraction in fliers and sound-producers as a function of contraction frequency. The circles are for fliers with synchronous muscle, the squares are for fliers with asynchronous muscle and the triangles are for singing species. All data are for insects, and the line is the range of frequency used by the tailshaker muscle of the rattlesnake (reprinted with permission from Nature 383, 71. © 1996 Macmillan Magazines Ltd). The inset shows the data for singing species and the rattlesnake (horizontal bar).