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 



