INFLUENCE OF WINDS ON DIFFUSION. 83 



At about three o'clock in the afternoon of that day, which was very hot, the people 

 oi this village were surprised by a shower of Aphides, or smother-flies, which fell in 

 these parts. Those that were walking in the street at that juncture found themselves 

 covered with these insects, which settled also on the hedges and gardens, blackening 

 all the vegetables where they alighted. My annuals were discoloured with them, and 

 the stalks of a bed of onions were quite coated over for six days after. These armies 

 were then, no doubt, in a state of emigration, and shifting their quarters; and might 

 have come, as far as we know, from the great hop plantations of Kent or Sussex, the 

 wind being all that day in the easterly quarter. They were observed at the same 

 time in great clouds about Farnham, and all along the vale from Farnham to Alton. 



Prof. Karl Sajo calls attention to the fact that many aphidids creep 

 to the crowns of the plant which they infest and then drop them- 

 selves at the proper moment into the boiling current of the storm. 1 

 In the studies made of Toxoptera many instances of this nature 

 have been observed. It will be recalled that Toxoptera graminum 

 appeared in swarms about Parma, Italy, in 1847 and again in 1852. 

 The notes of Mr. C. N. Ainslie, made on Toxoptera in Oklahoma 

 and Kansas, contain very many similar interesting records. 



At Kingfisher, Okla., under date of March 27, 1907, Mr. Ainslie 



makes this record. 



Toxoptera flying to-day by the million. The air was full of the migrants, and 

 farmers who drove to town were covered on the windward side to their annoyance. 

 The aphides seem for the most part to fly low, but the wind hurried them at such a 

 rapid rate that they might easily have been invisible when higher in the air. 



The following day his field notes contained these significant state- 

 ments: "Large numbers of Toxoptera on the wing to-day, always 

 moving north," and as those who have studied the species will 

 understand, the most interesting statement was that "A heavy 

 thunder shower passed by on the north last night, 30 miles away, 

 and a few drops fell here." In the same locality, under date of 

 April 3, he states that winged individuals of Toxoptera were taking 

 to wing freely, for he had observed many leaving the blades in the 

 fields and taking flight. Again, under date of April 6, "The air is 

 full of flying Toxoptera to-day, going northeast with a light breeze. 

 They do not fly high, from 2 to 15 feet." (The temperature at 

 Wichita, 30 miles north, was from 42° to 57° F.) At Wellington, 

 Kans., April 24 (with Wichita temperature 45° to 81° F.), he found 

 Toxoptera flying by the million and farmers driving to town had to 

 shelter their eyes from the swarm. On April 29, he records these 

 observations : 



Yesterday afternoon was warm for awhile (41° to 63° F. at Wichita), light north- 

 west breeze. Toxoptera took wing in immense numbers for 15 or 20 minutes, drift- 

 ing southwest, but soon saw their mistake and the air cleared. This is the only 

 instance seen by me when these aphides failed to fly north. The wind did not carry 

 them far this time. A Sunday ball game was in progress when they flew, and I was 

 told that the myriads of aphides interfered with the game; it was like trying to play 

 in a snowstorm. 



i The Wanderings of Insects. Prometheus, vol. 1, by Prof. Karl Sajo, 



