THE OUTBREAK OF 1907. 31 
following day large numbers of Toxoptera were on the wing, always 
moving north. In a field of oats, sown in February, the plants had 
hitherto been very thrifty, but at this time in a great many of the 
drill rows the plants were about dead for a space of 8 or 10 feet, and 
in case of later sown fields the plants were all fast dying under the 
attack. There was becoming gradually apparent a fact of consider- 
able importance regarding the relative number of winged forms in 
the fields. In oats fields where the food was succulent and good it 
was difficult to find a single pupa, while in older and less succulent 
wheat, perhaps within a yard of the oats, pupss would form 75 or 80 
per cent of the population of the blades. This was afterwards verified 
repeatedly by observation and by actual counting; indeed, through- 
out the entire spring this fact seemed to be substantiated. 
From March 31 to April 3 Mr. Ainslie carefully examined fields of 
wheat and oats in the vicinity of Wellington, Kans. He found wheat 
fields invariably evenly infested with Toxoptera though nowhere in 
any great numbers. Many of these were winged adults, indicating 
that they were migrants, and the young about them clearly evidenced 
a recent invasion. No dead areas were observed in the fields north 
of Pond Creek, Okla., but between Kingfisher and this point the 
circular dead spots were plainly in evidence. These dead areas, 
(PI. I, fig. 2), from their regularity in the field, plainly indicated the 
rows of oats shocks of the fall previous and were clearly to be seen 
where the oats had been shocked and allowed to stand through a period 
of wet weather. This generally produced a vigorous growth of 
volunteer oats when the shocks were finally stacked or removed, 
and in this young grain the Toxoptera seem to have had an early 
start. In some cases it was easily possible to observe these spots 
all over a field, although the volunteer oats were rarely entirely 
killed — perhaps only changed to a reddish color. The infestation 
seemed to be more marked in the wheat in the vicinity of these spots, 
and later the Toxoptera swarmed about these places. 
It may be noted that these observations of Mr. Ainslie in north- 
western Arkansas, southern Kansas, and northern Oklahoma were 
made upon the same dates as those of the junior author about Fort 
Worth, Tex., and at Hobart in southern Oklahoma, thus covering 
a latitude of nearly 400 miles. 
Mr. Ainslie returned to Kingfisher, Okla., April 3, and was joined 
there by the junior author on the 8th of the same month, where a 
number of experiments were carried out in the field, the results of 
which are given in the proper place. By- the 8th of the month para- 
sitized Toxoptera was found excessively abundant in the fields, in 
evidence of which a case was noted where a section of a leaf of wheat 
1J inches in length carried 43 brown, parasitized individuals. Mr. 
Ainslie left Kingfisher, Okla., for Wellington, Kans., on the following 
