Excerpt from A Monograph of the Jumping Plant-Lice or Psyllidae of the New World As the work progressed and other large collections were studied, many unsatisfactory features were found in this system and a great many difficulties encountered. Some of these have been mentioned in more or less detail in my former papers on this group. It became apparent that any classification based principally on wing venational characters would be artificial and unsatisfactory. At the same time other characters were noted that seemed to be more fundamental and whose use in classification seemed to place together certain obviously related genera. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.