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 day, or some days after, there might come a north wind 

 with greatly reduced temperature, which, though not suffiqiently 

 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 by 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. 



Date 



(1907). 



Weather. 



Maxi- 

 mum. 



Mini- 

 mum. 



Di- 

 rec- 

 tion 

 of 

 wind. 



Ve- 

 loci- 

 ty of 

 wind. 



Date 



(1907). 



Weather. 



Maxi- 

 mum. 



Mini- 

 mum. 



Di- 

 rec- 

 tion. 

 of 



wind. 



Ve- 

 loci- 

 ty of 

 wind . 



Feb. 1 



Clear 



°F. 



81 

 83 

 49 

 56 

 47 



00 



68 

 73 

 68 

 72 

 74 

 78 

 71 

 70 

 77 

 80 

 80 

 76 

 79 

 80 

 80 

 79 

 67 

 66 

 68 

 81 

 80 

 73 

 77 



°F. 

 63 



48 

 38 

 33 

 28 

 34 

 39 

 33 

 38 

 42 

 44 

 36 

 46 

 50 

 40 

 44 

 48 

 53 

 52 

 44 

 47 

 52 

 62 

 56 

 48 

 49 

 63 

 64 

 52 

 43 



SE. 



N. 



N. 

 NE. 

 NE. 

 NE. 



N. 



N. 



S. 



N. 



N. 



S. 



s. 



N. 

 N. 



sw. 



RE. 

 SW. 



N. 

 SW. 



s. 



SE. 



SE. 

 NE. 



N. 

 SE. 



S. 



N. 

 NW. 



S. 



Miles 

 per 

 hour. 

 11 

 26 

 22 

 20 

 19 

 15 

 22 



7 

 15 

 22 

 10 

 10 

 15 

 24 



9 

 11 

 10 

 14 

 18 

 10 

 17 

 19 

 15 

 22 

 19 



7 

 15 

 30 

 27 

 14 



Mar. 3 



4 



5 



6 



7 



8 



9 



10 



11 



12 



13 



14 



15 



16 



17 



18 



19 



20 



21 



22 



23 



24 



25 



26 



27 



28 



29 



30 



31 



Clear 



°F. 

 80 

 82 

 84 

 85 

 84 

 82 

 80 

 80 

 85 

 87 

 80 

 70 

 70 

 76 

 88 

 88 

 89 

 89 

 88 

 87 

 86 

 88 

 87 

 86 

 88 

 88 

 73 

 72 

 70 



°F. 

 49 

 56 

 64 

 64 

 64 

 66 

 66 

 57 

 65 

 65 

 70 

 47 

 42 

 46 

 66 

 64 

 62 

 63 

 63 

 64 

 66 

 67 

 68 

 68 

 69 

 68 

 55 

 55 

 52 



SE. 

 SE. 



S. 

 SE. 



S. 

 SE. 



S. 



w. 



SE. 



s. 



NE. 



N. 

 NE. 

 SE. 

 SE. 

 SE. 

 SE. 

 SE. 

 SE. 

 SE. 



S. 

 SE. 

 SE. 

 SE. 

 SE. 

 SE. 



N. 



N. 



N. 



Miles 

 per 

 hour. 

 13 



2 



Fair 



do 



15 



3 



Cloudy 



Fair 



Fair 



16 



4 



do 



18 



5 



do 



Clear 



15 



6 



Cloudy 



Fair 



Fair 



18 



7 



do 



16 



8 



Clear 



do 



23 



9 



do 



do 



21 



10 



do 



do 



21 



11 



...do 



..do 



17 



12 



do 



do 



36 



13 



do 



Clear 



23 



14 



...do 



....do 



14 



15 



.. ..do 



...do 



18 



16 



do 



do 



Fail' 



...do 



15 



17 

 18 



do 



....do 



15 



17 



19 



Clear 



do 



24 



20 



do 



do 



20 



21 



do 



Fair 



....do 



15 



22 



do 



16 



23 



Cloudy 



do 



do 



do 



Fair 



do 



Fair 



18 



24 



....do 



20 



25 



....do 



17 



26 



do 



20 



27 

 28 



Cloudy.. 

 Fair 



26 



14 



Mar. 1 



Clear 



do 



Clear 



22 

















