THE CLOVER ROOT BORER 17 
May 2, and May 16, respectively, were 68°, 79°, 82°, and 77° F., 
each being the maximum attained since the preceding examination. 
The same screen, except for a reduction in width.to 18 inches, was 
again erected on May 1, 1917, at the western edge of a recently plowed 
clover field in the same location as in the previous season. Counts 
of borers were made from May 2, when none were found, to June 12, 
this date included, at intervals of from 2 to 12 days; and, finally, 
after a further interval of 15 days, on June 27. Table 3 presents these 
counts in detail, in the same manner as the counts are presented in 
Table 2. Maximum temperatures and their dates of reading at 
Forest Grove were as foliows, each being the maximum attained since 
the last previous reading: May 1, 61°; May 2, 67°; May 8, 74°; 
May 10, 65°; May 18, 64°; May 23, 65°; May 28, 75°; May 31, 72°; 
June 6 and 7, 76° F. 
Of the 214 borers caught on the screens in 1916, 140, or about 65 
per cent, were counted on May 13, 11 days after the last previous 
count. A majority of the separate counts of that date, for the 
opposite sides and the several sections of the screen, were more than 
half the corresponding totals for the season. These were probably 
caught on the afternoon of May 2, after the examination of the screen 
in the morning of that date, and on May 3, 4, and 12, when the maxi- 
mum temperatures were 82°, 74°, 76°, and 67° F., respectively. The 
temperature did not rise above 60° I. on the other days 
Similarly, as shown in Table 3, on May 29, 1917, a date 16 days 
later than that of the maximum count for 1916, the total count of 
borers on the screen was 658, or approximately 70 per cent of the 
total for the season. The borers counted at that time were caught 
in the five days from May 24 to May 29, the maximum temperatures 
for each date being 60°, 57°, 64°, 71°, 75°, and 75° F., including the 
maxima of May 24 and May 29. Nearly every one of theseparate 
counts for that date was a large majority, two-thirds or more, of the 
corresponding totals. It will be observed that thescreen caught in 1917 
more than four times the number of borers caught by it in 1916, and 
in a shorter interval of time. This may be accounted for on the 
theory that the borers left the plowed clover east of this screen in 
ereat numbers on the warm days of May 27, 28, and 29, 1917, after 
a preceding interval of cool weather. In flying most of them flew 
against the prevailing westerly winds. The fact that the screen in 
1916 was east of plowed clover and the prevailing winds are westerly 
at this time may account for the fact that fewer borers were caught 
in that year. 
As to the height to which borers fly, it is plain that numbers of 
them fly 40 or 50 feet above the surface of the ground. Of those caught 
on the 50-foot screen in 1916, approximately 13 per cent flew more 
than 40 feet, 19 per cent more than 30 feet, 31 per cent more than 
20 feet, and 69 per cent more than 10 feet above the ground. The 
corresponding percentages for 1917 were 8, 18, 37, and 61; and for 
both seasons combined, 9, 18, 36, and 63. 
Near Forest Grove, in the season of 1917, an experiment with the 
small bannerlike screens, 18 by 36 inches, placed one each on the 
north and west sides of a field of spring-plowed clover gave interest- 
ing data as to the numbers of root borers flying from this field on 
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