30 
BULLETIN 19, U. S. DEPARTMENT OF AGEICULTUKE. 
Table XII. — Maximum, minimum, and average temperatures taken at the field labora- 
tory, North East, Pa., from June 1 to October 31, inclusive. 
June. 
Dav of 
the 
month. 
Julv. 
August. 
September. 
October. 
° F. 
50 
64 
59 
60 
44 
54 
46 
38 
45 
58 
55 
° 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. 
F. 
F. 
72 
53 
62.5 i 
75 
58 
66.5 1 
82 
68 
75.0 1 
83 
68 
75.5 
84 
68 
76,0 
84 
70 
77.0 
92 
72 
82.0 
87 
71 
79.0 
85 
73 
79.0 
80 
72 
76.0 
87 
69 
78.0 
85 
66 
75.5 
82 
65 
73.5 
87 
69 
78.0 
83 
73 
78.0 
92 
61 
76.5 
74 
63 
68.5 
77 
63 
70.0 
82 
57 
69.5 
65 
52 
58.5 
75 
63 
69.0 
77 
63 
70.0 
73 
54 
63.5 
72 
60 
66.0 
70 
68 
69.0 
75 
61 
68.0 
75 
52 
63.5 
70 
57 
63.5 
75 
64 
69.5 
73 
57 
65.0 
72 
52 
62.0 
° F. 
59.0 
61.0 
63.5 
57.0 
59.5 
60.0 
63.0 
66.0 
72.0 
72.5 
68.5 
73.5 
66! 
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 
83 
80 
3 F. 
74.5 
77.0 
rs.o 
T4.0 
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 
77 o4 
69 49 
58 43 
71 51 
67 56 
55 
39 
63 
46 
71 
56 
63 
52 
54 
45 
71 
48 
<y> 
56 
56 
43 
44 
41 
48 
44 
54 
44 
56 
41 
60 
47 
,0 
00 
63 
64 
54 
44 
F. 
5.3. 
54.5 
62.0 
61.5 
60.5 
59.0 
50.5 
61.0 
61.5 
66.0 
64.0 
52.5 
52.0 
49.5 
47.0 
54.5 
49.5 
59.5 
60.5 
49.5 
42.5 
46.0 
49.0 
48.5 
53.5 
02.5 
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, 
