A MONOGRAPH OF THE JUMPING PLANT-LICE OR PSYLLIDiE OF THE NEW WORLD. By David L. Crawford/ Of the Laboratory of General Biology, Cornell University, Ithaca, New York. INTRODUCTION. The family PsyUidse, or the Jumpmg Plant-lice, have received com-paratively little attention in the New World, especially from the systematic point of view. A relatively small number of species have been described, but no serious attempt has been made to relate the several genera represented by these species. The European forms have received a great deal of attention, notably by Dr. Franz Loew and now by Dr. Karel Sulc. Others have made some contributions, but in a much more unrelated manner. With the two names just mentioned, the name of Witlaczil should not be omitted. Some very good work on the internal anatomy has been done by him. Until 1848 only a few genera were recognized, most of the species being placed in Psylla. At that date Foerster divided Psylla into several smaller genera, most of which are still vaUd. In 1878 Loew pubUshed his Zur Systematik der PsyUoden, in which he established several additional new genera and tabulated four subfamiUes — Triozinse, PsyUinse, Aphalarinse, and Liviinae. With the exception of the latter, these were separated from each other on the basis of wing venation characters. In his subsequent work he followed this same system of classifica-tion and there soon appeared more subfamdies and many more genera. Other workers during and since his time have employed his system of classification, also. The basic diagnostic characters used by Loew in this system were largely venational. The presence or absence of the cubital petiole (M + Cu), and the relative length of this petiole, when present, and the radial stem (or discoidal subcosta), were the two principal characters for the separation of subfamiUes. In undertaking systematic work on a large collection of PsyHidas some four years ago, Loew's system of classification was employed because it was practically the only one to be used. The collections before me were very large and contaiued very large series of speci-mens of many species, in which there would naturally be more or 1 Contribution from the Entomological Department of Cornell University, Ithaca, New York. This su-persedes the former papers by the author on this group. 1
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