322 Forty- SIXTH Report on the State Museum 



color at different ages, and in different seasons of the year, being of a 

 ^ull crimson color, shaded with black in the spring, when it conies forth 

 to lay its eggs. Not having seen any of our pear-tree Psylke in their 

 spring dres"", I can not say whether they agree with those of Europe in 

 being of the same crimson color at this season of the year." 



The PysUa Referred to P. pyricola. 



In the bibliography herewith given, all of our earlier writers have 

 accepted it as probably identical with the Psylla pyri of Europe, with 

 the sole exception of its description and illustration by Dr. Barnard 

 under the name of P. pyrisuga. Dr. Riley, I believe, was the first to 

 detect specific characters separating it from that species, and to refer 

 it to P. pyricola — one of the three closely allied species which attack 

 and injure the pear tree in Europe, of which, according to Dr. Loew, 

 '^^ P. pyrisugo/F oQT^tQV is found throughout Central Europe in large 

 numbers annually, and is a great pest; P. pyri Linn, is comparatively 

 rare, appearing in small colonies, but is widely distributed; P. pyricola 

 Foerster occurs in some localities in large numbers, particularly infesting 

 dwarf pears, and often occasions considerable damage."* 



In his reference to P. pyricola Dr. Riley states: " This is the Pear- 

 tree Psylla of our Northern and Western States, and its reference to 

 -Foerster's species is made after comparisons with European specimens 

 .received from Meyer-Dilr and Lichtenstein."f 



The identity of our species with any of the European has been 

 ■^questioned by some of our writers, but for the present, at least, we 

 must accept Dr. Riley as authority, he having recently, in reply to 

 inquiry made, written me even more explicitly than quoted above: 

 *** The common pear-tree Psylla of New York and Massachusetts is 

 anquestionably P. pyricola Foerst., and agrees perfectly with European 

 specimens sent me by Dr. Loew." 



Its Recent Multiplication in the Hudson River Valley. 

 Like many other of our insect pests, the Pear-tree Psylla, from time to 

 time, and for a longer or shorter term of years, is favored with condi- 

 tions peculiarly fitted to its increase, which are again followed by cor- 

 responding periods of almost entire exemption from its presence. 

 Thus, according to Dr. Plumb, it was not noticeably present in his 

 orchards for the ten years following the year 1838, previous to which 

 it had annually been very destructive. 



* From an abstract by Riley-Howard in Insect Life, iv, 1891, p. 127, from Dr. Loew, loc. cit, 

 ■ A Proceedings of the Biological Society of Washington, li, 18S4, p, 69. 



