242 Agricultural Experiment Station, Ithaca, N. Y. 



The weather at the opening of spring greatly influences the time 

 of appearance of the hibernating brood, and the date of the lay- 

 ing and hatching of the eggs. An overlapping of the broods 

 occurs, so that after June first all stages of the insect, eggs, 

 nymphs, and adults may be seen on the trees at the same time. 

 This Is due to the facts that tlie eggs of any female are not all 

 laid the same day, and thus do not hatch at th.e same time; and the 

 duration of the stages of the njaiiphs varj' slightly, thus varying 

 the time of the appearance of the adults. 



Observations at the insectary and in the field have sihown tliat 

 diu-ing the present year, 1892, there ha? been at least four broods 

 of the pest. The hibernating adults oviposited in April, and 

 adults of this spring brood appeared about June fifteenth. The 

 adults of the summer broods were t^ie moRt numerous on or about 

 the following dates: July twentieth, August twentieth, and Sep- 

 tember twenty-fifth; or a brood appeared about once a month. 

 All stages of the insect were found on the trees as late as Septem- 

 ber t\N'entieth; evidently vdnter must overtake some of them before 

 they reach the adult state. The adults emerging in September 

 and later were found to be all of the hibernating form. 



Peculiarities of the winter brood. — The hibernating adults found 

 in December, 1891, were so different from the descriptions of 

 Psylla pyricola that they were believed to belong to another spe- 

 cies, perhaps new.* A'S^ien the summer adults appeared, however, 

 they were readily recognized as the old ofi'ender Psylla pjTicola. 

 The hibemating adults differ from the summer adults in size, being 

 nearly one-third larger; in their much darker coloring, the ciim- 

 son becoming a dark reddish brown; and especially in the color- 

 ation of the front wings. The summer foniis or typical pATicola, 

 have the veins, even in darker specimens, of a light yellowish 

 brown color, and the whole front wing has a slight yellowish 

 tinge. The veins of the wings of the hibernating adult are 



* Well marked specimens were submitted to Dr. C. V. Riley, the recognized authority upon 

 American Payllids. In his reply he says : " Your Pear-tree Psylla is a species which I have never 

 seen before and which is not in my collection. Its general appearance is not that of our native 

 species Psylla, and it has, no doubt, been introduced from Europe. It is uiuiuestionably different 

 from P. pyricola which I have from Ithaca, n". Y.. Connecticut and Massachusetts. Owing to 

 the difference in the genital apparatus of the male it can not be identical with P. pyrisuga and 

 pyrl, but agrees perfectly with the description of P. simulans." 



