5 



Northern States and westward to the Mississippi, and has yet, during all this 

 time, rarely been reported as injuriously abundant, argues that the conditions 

 favorable to its increase are seldom met with. Its complete disappearance in 

 one orchard, after a year of excessive abundance, is a case in point ; and the 

 excessive multiplication in New York State in L89] was followed the next year, 

 according to .Mr. Slingerland, by scarcely any injury in comparison. The reasons 

 for the sudden multiplication and quite as sudden disappearance of this pest are 

 difficult to give. A succession of two or three winters favorable to hibernation 

 probably leads to the unusual increase, and the resulting attack brings the trees 

 into a condition which is probably prejudicial to the insect. With the later 

 summer broods, as pointed out above, the condition of the leaves which have 

 been seriously attacked by the earlier broods is such that the insect becomes 

 markedly less abundant later in the season. The green, succulent foliage of the 



Fio. i.—Chrysopa oculata Say : a. eggs; 6, Eull-grown larva : .■. foot of same: </. same devouring a 

 I'sylla ; /', cocoon; f, adult insect : g, head of same; h. adult, natural size— all enlarged except 

 h i original). 



young spring growth is especially favorable, and when the leaves become 

 haidened and mature, and especially dry and innutritions, from having been 

 already sapped of their vitality, they are distasteful and unsuited to the develop- 

 ment of the later hi' Is. 



The parasitic and predaceous insects also become very efficacious by mid- 

 summer, and a very interesting experience in the case of the Maryland invasion 



will be now noted. 



NATURAL ENEMIES. 



No enemy for this insect among the parasitic and predaceous species has, 

 previous to this year, been recorded. < >n my first visit to the Maryland orchard 

 I was shown what was taken to be the egg of the I'sylla, which proved, however, 

 to he the egg of a common lace-winged fly, Chrysopa oculata Say. The mistake 

 was a very natural one. for the eggs occurred in extraordinary number- through- 



