New York Agricultural Experiment Station. 939 



above freezing, especially if the sun shines, will bring the flies from 

 their hiding places under the rough bark or in crevices in it and 

 send them to fruit spurs. With settled cold the flies remain dormant 

 until warm days again occur in late March or early April. 

 They then seek the bud spurs and may remain active continuously 

 if the temperature remains above freezing, or may be chilled into 

 quiescence if the mercury drops again. Soon, however, they mate, 

 and egg-laying begins, the time for this varying with the weather. 

 The dates of the beginning of oviposition for the four years 1910-1913, 

 inclusive, were, in order, April 2, April 14, April 15 and March 21. 

 While egg-laying does not have a very constant relationship to the 

 condition of pear buds, some are always laid before the cluster 

 buds break, and most of them before the tips of these buds have 

 separated. This is an important fact to remember, for it is the 

 index of the proper time to attack the insects — a most essential 

 factor in control measures. 



The eggs are orange-yellow in color and very small, so that single 

 ones cannot be distinguished by the eye; but they are often deposited 

 in such numbers that they appear as distinct orange spots or patches. 

 The earliest eggs are laid on the wood, in crevices in the bark around 

 the bases of the blossom buds or on the stems, or in some cases on 

 watersprouts. Oviposition is more often on the under side than 

 on the upper side of the stems and bud spurs. Later, when foliage 

 is unfolded, eggs are laid on the leaves. Egg-laying lasts about two 

 weeks, the time again varying with the weather; and the date of 

 hatching is also dependent on the same factor. Under artificial 

 conditions in the warm laboratory, the larvae may emerge in eight 

 days, or outdoors, in cool weather, it takes ten days longer; while 

 warm days hasten development. This frequently makes many 

 early-laid and late-laid eggs hatch at the same time, as on April 19, 

 1910, May 2, 1911, May 4, 1912, and April 10, 1913, when the young 

 larvae emerged in countless numbers. 



The larvae are quite unlike the adult flies, as shown in Figs. 1 

 and 2 of Plate I, which represent the five stages of their development, 

 the last being the well-known " hard-shells." These nymphs or 

 larvae are rather sluggish, wingless creatures quite similar in all 

 stages and always easily identifiable by their bright red eyes. Suc- 

 cessive broods of these nymphs emerge about a month apart through- 

 out the summer and continue the harmful work of the first brood. 



Of course, spraying is practically the only 



Remedies possible method for controlling the pear psylla — 



suggested. spraying with a contact insecticide, since the 



insects feed from beneath the surface and cannot, 



therefore, be poisoned. But the older sprays and methods proposed 



have not proven thoroughly satisfactory, as these were usually 



attempts to control the psyllas after the larvae were present in large 



numbers on opened buds and developing leaves. The difficulty of 



