This volume is the proceedings of the IX International Conference on E phemeroptera and the XII International Symposium on Plecoptera, held i n Tucuman, Argentina. Divided into comprehensive thematic sections, th e early sections cover studies on ecology and behavior ranging from li fe cycles and general biology to genetic divergence and vibrational co mmunication, while the latter sections reveal the diversified studies being developed worldwide. This book will be useful for beginners and specialists, providing important data for ecological, distributional, morphological, and biogeographical studies.