﻿30 



BULLETIN 19, U. S. DEPAETMENT OF AGEICULTUBE. 



Table XII. — Maximum, minimum, and average temperatures taken at the field labora- 

 tory, North East, Pa., from June 1 to October 31, inclusive. 



June. 



Day of 



the 

 month. 



July. 



August. 



September. 



October. 



° F. 

 60.0 

 71.0 

 68.0 

 67.5 

 56.5 



60.5 

 57.0 

 48.5 

 55.5 

 61.5 



62.5 

 69.0 

 58.5 

 54.5 

 69.0 



64.5 

 67.0 

 59.5 

 56.5 

 60.5 



64.0 

 63.0 

 49.0 

 60.0 

 69.5 



70.5 

 68.0 

 74.5 

 70.5 

 71.0 



° F. 

 62.5 

 66.5 

 75.0 

 75.5 

 76.0 



77.0 

 82.0 

 79.0 

 79.0 

 76.0 



78.0 

 75.5 

 73.5 

 78.0 

 78.0 



76.5 



68.5 

 70.0 

 69.5 

 58.5 



69.0 

 70.0 

 63.5 

 66.0 

 69.0 



68.0 

 63.5 

 63.5 

 69.5 

 65.0 

 62.0 



° F. 

 59.0 

 61.0 

 63.5 

 57.0 

 59.5 



60.0 

 63.0 

 66.0 

 72.0 

 72.5 



69.5 

 68.5 

 73.5 

 69.0 

 66.0 



64.0 

 59.5 

 66.5 

 72.5 

 67.0 



70.0 

 68.0 

 70.0 

 63.0 

 75.5 



74.0 

 70.0 

 57.0 

 56.5 

 57.5 

 61.0 



87 



° F. 



74.5 

 77.0 

 75.0 

 74.0 

 77.5 



76.5 

 78.0 

 66.5 

 68.5 

 75.5 



79.0 

 66.0 

 60.5 

 73.0 

 74.5 



71.0 

 55.5 

 64.0 

 66.5 

 61.5 



62.5 

 72.0 

 66.5 

 58.5 

 65.0 



68.5 

 55.5 

 48.5 

 55.0 

 43.5 



° F. 

 53.0 

 54.5 

 62.0 

 61.5 

 60.5 



65.5 

 59.0 

 50.5 

 61.0 

 61.5 



66.0 



64.0 

 52.5 

 52.0 

 49.5 



47.0 

 54.5 

 63.5 

 57.5 

 49.5 



59.5 

 60.5 

 49.5 

 42.5 

 46.0 



49.0 



48.5 

 53.5 

 G2.5 

 54.5 

 49.0 



SUMMARY OF SEASONAL HISTORY OF THE GRAPE LEAFHOPPER. 



The grape leafhopper (see fig. 1, p. 1) hibernates as an adult 

 among accumulations of leaves and trash in vineyards, but mostly 

 in adjoining woodlands, hedgerows, and pastures. It becomes active 

 during the first warm days of spring and commences feeding on 

 the new growth of almost any of the plants with which it comes 

 in contact. With the unfolding of the grape leaves there is a gen- 

 eral migration of the insect to the vineyards. In normal seasons 

 this takes place about the middle of May in the vineyards of the 

 Lake Erie Valley. After feeding for a few days the leaf hoppers 

 mate, and oviposition commences early in June. The eggs are 

 deposited singly and are tucked under the epidermis beneath the 

 pubescence of the underside of the grape leaf. The average length 

 of the egg stage is from 11 to 15 days. The nymphs commence to 

 appear on the underside of the leaves about the 20th of June, and 

 by the end of the first week in July a large percentage of the first 

 brood has hatched and is present in one of the several nymphal stages, 



