基金Acknowledgements This work was supported by grants from the National Science Foundation and a visiting profes- sorship from The Leverhulme Trust to S.K.S., a University Royal Society Fellowship and Royal Society Equipment Grant to J.H, and grants from the Orthopterists' Society, the Beta Lambda Chapter of Phi Sigma, and the Graduate Student As- sociation of Illinois State University to C.B.W. We thank Gil Rosenthal, and two anonymous reviewers for constructive comments on the manuscript.