110 Agricultural Experiment Station, Ithaca, N. Y. 



active and are readily captured. The adults also feed upon the 

 sap by means of a sharp beak, but seem to have no favorite feed- 

 ing place. 



Egg-laying and habits during the summer. — In about a month 

 after emerging from the ^^^ in the spring, the nymphs become 

 full grown and at the last casting of the skin the aduit insects 

 appear. 



This lirst brood, appearing about June 10, and all subsequent 

 summer broods of the adults, differ strikingly from those that 

 hibernate. The winter forms differ in size, being nearly one-third 

 larger, in their much darker coloring, and especially in the darker 

 coloration of the front wings. Thus, in this pear psylla, we have 

 a case of true dimorphism ; the winter form had been described as 

 a distinct species, Psylla simulans. 



In about a week after their transformation from the nymph stage^ 

 the summer adults copulate and begin laying eggs for another 

 brood. These eggs do not differ from those laid by the winter 

 forms, but they are laid singly or in groups, not on the bark of the 

 twigs, but on both sides of the leaves, tucked in among the hairs 

 along the midrib or adroitly placed in the notches of the toothed 

 edge of the leaf. They hatch in from eight to ten days. 



A careful study was made of one generation of the insect in 

 1892 and the many interesting details then learned have been re- 

 corded in Bulletin 44. It was found that the nymphs cast their 

 skin live times, at intervals of from three to seven days, the adult 

 insect appearing at the fifth or last moult. So life-like were some 

 of the cast skins as they were left on the leaves by the nymphs 

 that it often required close examination with a lens to determine if 

 the object was alive or only a nymph's cast-off garment. In each 

 stage the nymphs secreted globules of honey-dew several times 

 larger than themselves. Although the adults feed, they do not 

 grow nor do they seem to secrete any honey-dew, but void consider- 

 able quantities of a whitish excrement. The summer adults pro- 

 bably live for less than a month, while those that hibernate remain 

 alive for at least six months. 



Numljer of hroods. — Our observations indicate at least four 

 broods in this State ; the adults were the most numerous on or 

 about June 15, July 20, August 20 and September 25, or a brood 



