CORNELL UNIVERSITY EXPERIMENT STATION BULLETINS. 261 



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upward, thus bringing the forceps (Fig. 5,/) in a position to grasp the 



upper genital plate (Fig. 6, u) of the female; 

 this allowed the penis (Fig. 5, p) to enter 

 between (at e. Fig. 6) the valves of the female 

 organ, and the upper male genital plate (Fig. 

 5, u) to simply lie along the venter of the lower 

 genital plate (Fig. 6, /) of the female. A 

 further slight side twist of the abdomen 

 Fig. 6.— Abdomen and genital or- brought the male heside or in some cases upon 

 l^al;f.eg|-8heS:iowe;^:^tti the female; the wings of both remained in a 

 plate; a. upper genital plate. resting position. The hair lines beneath fig- 



ures 5 and 6 represent the natural length of the abdomen, including the 

 genital organs. Copulation lasts for several minutes, and one male may 

 copulate with more than one female. 



The number of broods. — The pest may be said to be many-brooded, the 

 number varying with the conditions of the season. The weather at the 

 opening of spring greatly influences the time of appearance of the hiber- 

 nating brood, and the date of the laying and hatching of the eggs. An 

 overlapping of the broods occurs, so that after June 1 all stages of the 

 insect, eggs, nymphs, and adults may be see on the trees at the same time. 

 This is due to the facts that the eggs of any female are not all laid the 

 same day, and thus do not hatch at the same time; and the duration of the 

 stages of the nymphs vary slightly, thus varying the time of the appear- 

 ance of the adults. 



Observations at the insectary and in the field have shown that during 

 the present year, 1892, there has been at least four broods of the pest. The 

 hibernating adults oviposited in April, and adults of this spring brood 

 appeared aboat June 15. The adults of the summer broods were the most 

 numerous on or about the following dates, July 20, August 20, and Sep- 

 tember 2o: or a brood appeared about once a month, All stages of the 

 insect were found on the trees as late as September 20; evidently winter 

 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 species, perhaps new.* When 

 the summer adults appeared, however, they were readily recognized as the 

 old offender Psylla pyricola. The hibernating adults differ from the sum- 

 mer adults in size, being nearly one third larger; in their much darker color- 

 ing, the crimson becoming a dark reddish brown; and especially in the 

 coloratiotti of the front wings. The summer forms or typical pyricola, 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 invariably of a dark brown or black color; the 

 front wings are quite transparent with more or less blackish shades in the 

 cells and a blackish shade in the basal cell along the whole suture of the 



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

 Psyllids. In his reply he pays: "Your pear tree Psylla is a species which I have never sf«n before and 

 •which is not in my collection. Its general appearance is not that of onr native species of Psylla and it 

 has, no doubt, been introduced from Europe. It is unquestionably different from F. pyricola which I 

 have from Ithaca, N.Y., Connecticut, and Massachusetts. Owing to the difiference in the genital appara- 

 tus of the male it can not be identical with F. pyrisuga and pyri. but agrees perfectly with the descriptioo 

 of P. simulans.'' 



