New York AgricultuRx^l Experiment Station. 



355 



Fig. 27. Eggs, enlarged, of pear psylla. 



while the larger end is attached to the bark by a short stalk. (Fig. 27.) 

 The eggs are deposited about the bases of buds, in old leaf scars 

 and on the bark of twigs and 

 smaller branches. In western 

 New York the eggs may usually 

 be seen during the first week 

 in April or about one week 

 after the flies emerge from 

 their winter quarters. In some 

 seasons the eggs are so abun- 

 dant as to cause the bark to 

 have a yellowish appearance 

 in spots. The newly-hatched 

 nymph is a small, pale, soft- 

 bodied creature with a single 

 pair of red eyes, and its shape 

 and the character of its exter- 

 nal structures are represented 

 in Plate XVIII, fig." 1. The 

 young psylla undergoes several 

 changes or molts. (Plate 

 XVIII, figs. 2,3,4.) With each 

 transformation the insect increases in size, and in the fifth stage 

 it appears as a flat oval creature of a brownish color, with whitish 

 or greenish mottling and with conspicuous dark brown wing pads. 

 (Plate XVIII, fig. 5.) These are known to most pear growers as 

 " hard shells." The nymphs are sluggish creatures 

 and cling closely to the surface of the leaves and 

 fruit. The adult is an active four-winged insect 

 measuring about one-tenth of an inch in length. 

 It has been compared to a miniature seventeen-year 

 locust. (Fig. 28.) 



The adults or flies live over the winter preferably 

 hidden in crevices under the loose bark of the trunks 

 and larger branches of the trees. They have also 

 been observed under fallen leaves or other debris 

 which may be on the ground. During the first warm 

 days of spring, even as early as the latter part of 

 March, these flies crawl out of their hiding places 

 and copulate. A change to colder weather checks 

 their activities, but with rising temperatures they 

 gradually distribute themselves over the trees by 

 creeping or by flying, when they lay their eggs. 

 If the weather continues warm the eggs are 

 quickly laid in large numbers, but if the weather is variable with cold 

 freezing rains or drops in temperature oviposition may extend over 



Fig. 28. Pear psylla; 

 winter adult, en- 

 larged. 



