122 KANSAS UNIVERSITY SCIENCE BULLETIN. 



edge of this family have been numerous and have added greatly 

 to our information on the subject. The first of these contribu- 

 tions was made by Forster, in 1848. He was followed by Flor, 

 Thomson, and Hartig, but not much of an advance was made 

 upon Forster's work until there appeared in 1879 a treatise, 

 "Zur Systematik der Psylliden," by Low; this, together with 

 other contributions by the same author, has long remained 

 authoritative. The researches of Low in the taxonomy and bi- 

 ology of the Psyllidse, together with the anatomical work of 

 Witlaczil, have much simplified the study of this family in 

 Europe. 



James Edwards, in "Hemiptera-Homoptera" (1896), treats 

 of four genera of the family, including twenty-eight species of 

 British Psyllidse, with tables for the separation of the genera 

 and species. He also illustrates these forms in color and gives 

 the typical wing venation of each genus. 



Maskel (1889) lists and describes four species of Psyllidse 

 from New Zealand, giving keys for separating the subfamilies 

 represented in that locality, and figures the larval, pupal and 

 adult stages, and some of their typical anatomical characters. 

 This paper contains more figures of these characters than any 

 other I have been able to find, and was quite useful from that 

 standpoint. This writer also discusses the use and taxonomic 

 importance of the difi'erent characters of the family. 



Froggatt (1903), in a paper on "Australian Psyllidse" de- 

 scribes eighteen species, mostly of the two genera Aphalaria 

 and Trioza. He figures the galls made by three species of the 

 latter genus. 



The reasons for the dearth of material in this country may be 

 found in the fact that the family Psyllidse, like some other little- 

 known groups, being composed of small and inconspicuous in- 

 sects, has not been largely collected and studied, two or three 

 species excepted. One of these, the pear Psylla, Psylla pyricola, 

 is of great economic importance in some localities, and has long 

 been known and its life history carefully worked out. The life 

 histories of these insects are very difficult to determine def- 

 initely, and since some of them are gall-formers, the biological 

 side of the work becomes still more complicated. Only about 

 three specialists have ever devoted much time to their study in 

 this country, among whom was C. V. Riley. In an article on 

 "The Psyllidse of the United States" (1883), he gives a resume 

 of the present knowledge of the family and its principal char- 



