68 BIOLOGICAL SOCIETY OF WASHINGTON. 



10. Psylla annulata Fitch. 



11. Psylla pyri (Linn.), Harris, Fitch, Glover, et al. 



12. Psylla pyrisuga (Forster), Barnard. 



1 3 . Psylla venusta O . - Sacken . 



14. Psylla celtidis-mamma Riley. 



15. Psylla tripunctata Fitch. 



1 6. Psylla rubi Walsh and Riley. 



1 7. Psylla diospyri Ashm. 



1 8. Psylla magnolia Ashm. 



Thus the number of described species amounts only to eighteen. 

 All other names occurring in Ashmead's list and in Walker's British 

 Museum list, as well as in cabinets, are manuscript names. Of the 

 eighteen species, four are merely synonyms, while one is an impor 

 tation. 



The synonyms have been principally caused by the fact that the 

 imagines of several species quite persistently occur on two or more 

 widely different plants : thus Psylla tripunctata is equally common on 

 Rubus and on Pinus ; but while this is true of the mature insects, 

 yet each species, so far as we yet know, is confined in its adolescent 

 stages to one genus of plants, and often to one species. 



According to the latest classification by Dr. Franz Low in his 

 paper, " Zur Systematik der Psylloden,"* our described species 

 must be placed as follows : 



I. SUB-FAMILY LlVIIN^E. 



1 . Livia vernalis, Fitch, (synonyms : Diraphia femoralis F. 



and D. calamorum F.). 



2. Livia maculipennis , Fitch. (Diraphia maculipennis Fitch.) 



This sub-family, which has but two representatives in Europe, is 

 at once recognizable by the flat, not prominent eyes, and by the 

 form of the antennae, the second joint being the largest. 



* Verhandlungen der zoologisch-botanischen Gesellschaft in Wien, 1878. 



