INFLUENCE OF WINDS ON DIFFUSION. 
85 
Still another factor of greatest importance is in the fact that, 
with a wind from a southern quarter, blowing strongly under a tem- 
perature sufficient to render Aphidius active, both Toxoptera and 
parasite would thus be carried on the wing perhaps miles to the 
northward and scattered over fields not previously seriously infested. 
The following da}^, or some days after, there might come a north wind 
with greatly reduced temperature, which, though not sufficiently 
cold to prevent immediate reproduction on the part of migrant 
Toxoptera, would yet keep the parasite inactive. That precisely 
these weather conditions do often occur during years of excessive 
abundance of Toxoptera is shown b}^ the following tables of the 
weather (Tables IV-VIII), while the dates thereof show conclu- 
sively that both Toxoptera and Aphidius were present and active. 
This last factor will be further discussed under natural enemies. 
These tables were compiled for us by the Weather Bureau. 
Table IV. — Maximum and minimum temperatures, with direction and velocity of wind, 
and character of the day, San Antonio, Tex., 1907. 
Di- 
Ve- 
Di- 
Ve- 
Date 
(1907). 
Weather. 
Maxi- 
mum. 
Mini- 
mum. 
rec- 
tion 
of 
wind . 
loci- 
ty of 
Date 
(1907). 
Weather. 
Maxi- 
mum. 
Mini- 
mum. 
rec- 
tion. 
of 
wind. 
loci- 
ty of 
wind. 
wind . 
Mies 
Miles 
per 
per 
°F. 
°F. 
hour. 
"F. 
°F. 
hour. 
Feb. 1 
Clear 
SI 
63 
SE. 
11 ' 
Mar. 3 
Clear 
80 
49 
SE. 
13 
2 
Fair 
83 
49 
48 
38 
N. 
N. 
26 
22 
4 
5 
do 
Fair 
82 
84 
56 
64 
SE. 
S. 
15 
3 
Cloudy 
16 
4 
Fair 
58 
47 
43 
33 
28 
34 
NE. 
NE. 
NE. 
20 
19 
15 
6 
7 
8 
do 
Clear 
85 
84 
82 
64 
64 
66 
SE. 
S. 
SE. 
18 
5 
do 
Cloudy -. 
15 
6 
Fair 
18 
7 
Fair 
60 
68 
39 
33 
N. 
N. 
22 
7 
9 
10 
do 
do 
80 
80 
66 
57 
S. 
w. 
16 
8 
Clear 
23 
9 
do 
73 
38 
S. 
15 
11 
do 
S5 
65 
SE. 
21 
10 
do 
68 
42 
N. 
92 
12 
do 
87 
65 
s. 
21 
11 
do 
72 
44 
N. 
10 
13 
do 
80 
70 
NE. 
17 
12 
do 
74 
36 
S. 
10 
14 
do 
70 
47 
N. 
36 
13 
do 
do 
78 
71 
46 
50 
s. 
N. 
15 
24 
15 
16 
Clear 
70 
76 
42 
46 
NE. 
SE. 
23 
14 
do 
14 
15 
do 
70 
40 
N. 
9 
17 
do 
88 
66 
SE. 
18 
16 
do 
77 
44 
sw. 
11 
18 
do 
88 
64 
SE. 
15 
17 
do 
80 
48 
SE. 
10 
19 
do 
89 
62 
SE. 
15 
18 
Fair 
80 
76 
79 
53 
52 
44 
SW. 
N. 
SW. 
14 
IS 
10 
20 
21 
22 
....do 
do 
do 
89 
88 
87 
63 
63 
64 
SE. 
SE. 
SE. 
17 
19 
Clear 
24 
20 
do 
20 
21 
do 
80 
47 
s. 
17 
23 
do 
86 
66 
S. 
15 
22 
Fair 
80 
52 
SE. 
19 
24 
do 
88 
67 
SE. 
16 
23 
Cloudy 
do 
79 
62 
SE. 
15 
25 
Fair 
87 
68 
SE. 
18 
24 
67 
56 
NE. 
22 
26 
do 
86 
68 
SE. 
20 
25 
do 
66 
48 
N. 
19 
27 
do 
88 
69 
SE. 
17 
26 
do 
68 
49 
SE. 
7 
28 
do 
88 
68 
SE. 
20 
27 
Fair 
81 
63 
S. 
15 
29 
Cloudy 
73 
55 
N. 
26 
28 
do 
Clear 
80 
73 
64 
52 
N. 
NW. 
30 
27 
30 
31 
Fair 
72 
70 
55 
52 
N. 
N. 
14 
Mar. 1 
Clear 
99 
2 
do 
77 
43 
S. 
14 
