MKTIIOl) OK INTRODUCTION, 



The suddenness and severity of the appearance of the Psylla, particularly in 

 the .Maryland instances, makes the question of its introduction one of consider- 

 able interest. Upon inquiry it was developed that in these cases the pear trees 

 had been obtained from a New York nursery in is*)(), or just al the time when 

 the Psylla appeared in such extraordinary numbers in New York State; and it 

 is unquestionably from this source that the Psylla was introduced. The young 

 trees secured in the fall of the year mentioned were undoubtedly infested with 

 hibernating Psyllas, as it was in the immediate vicinity of the point where these 

 trees were heeled in that the outbreaks occurred. In one case the insect seemed 

 to have gradually increased in numbers, reaching a destructive abundance in 

 the summer of 1894. The entire disappearance of the insect after the lirst year 

 in the other orchard is probably to be explained on the ground of some local 

 climatic condition. Such modifying influences are not unusual in the peach 

 belt of Maryland, as illustrated by the fact that orchards separated by only a few 

 miles, and with the same conditions as regards soil and variety of fruit, will 

 seemingly be so differently affected by 

 very local cold waves or storms that one 

 will be barren while the other will be full 

 of fruit. 



DESCRIPTION AND LIKE HISTORY. 



The Stages in the development- of this 

 insect are the egg, the larva, the nymph 

 or active pupa, and the adult or perfect, 

 winged insect. The egg (fig. 2, a) is 

 orange-yellow in color and so minute as 

 to lie almost invisible to the naked eye. 

 Its peculiar .-tincture is indicated in the 

 drawing— the short arm serving as its 

 attachment to the leaf. The newly 

 hatched larva is somewhat larger than 

 the egg and yellow in color, with crimson eyes, and has the characteristics indicated 

 at fig. 2, //. With each of the earlier molts the form approaches more and more 

 nearly the nymphal stage, which is represented in its final form at fig. 3. In 

 this stage the prominent features are the large wing pads. The general color is 

 dark reddish-brown, with the lighter areas indicated in the illustration— the eyes 

 remaining of a crimson color. In all the preparatory active stages the insect is 

 broad-oval and very much flattened, little, if at all, resembling the adult, hut 

 rather some scale insect, and is very sluggish. The adult (fi^'. 1) conies from 



the last nymph, and is a little, clear-winged insect, closely resembling the Cicada 

 or harvest fly vastly reduced. Like the latter, its wings close roof wise in repose. 

 Its color is reddish-crimson, with the brown or black markings indicated in the 

 illustration. The lasl or hibernating brood turns uniformly brownish black, with 

 bronzy eyes and dark wing veins, and was described as a distinct species (Psylla 

 simulans), but has been shown by Mr. Slingerland 1 to be merely a winterform, 



which result is continued by breeding records at this Department. 



The life history of the insect may be briefly summarized as follows: The 

 adults hibernate in crevices in the hark of pear trees 2 and emerge with the lirst 



'Bulletin 14, Cornell Agric. Exp. Station, Oct , L892 



- On potted trees in an unheated greenhouse the adults rested exposed en the twigs all winter 

 without making any attempt at concealment, ami began ovipositing early in March, the flrsJ 

 brood maturing early in April. The plants on which they wintered were, however, in time <>i 

 leafing, fully four \\cck> in advance of those on the grounds. 



2.— Pear-tree Psylla: a. egg; b, larva- 

 both greatly enlarged (original). 



