
(en cet bread eran? poe lscarn laces’ mane lige? T Tomak T 3 pee t T T T Tt 
210 7 
200 + 4 
log Y = 0.05321X + 0.9855 
190 F 5, = 0.007399 1 
180 + P <0.001 4 



4 4 4 4 ne 4 __} n aS pk 
5 6 7 8 PRA OI IDI 216 IS 16 pis 1B 
Miles 

Figure 1,--Total number of male P, sexta moths caught 
in each of 62 light traps from May 28 to August 4, 
1964, plotted against distance from center of trapped 
area, 


ob Y + 1 = 0.03926x = 0.46367 
5, = 0.003967 
P< 0.001 




Jl. a ae | wt j___ — a = A A .s - 
5 6 AP OB 9S 10 FI Sa) 32 14) USS 16 KF Ma” 19" Va 
Miles 
Figure 2,--Total number of female P, sexta moths 
caught in each of 62 light traps from May 28 to 
August 4, 1964, plotted against distance from center 
of trapped area, 

might have been caused by the traps or by other 
factors, 
The only known variable, other than the 
traps, that might have caused the depression 
197 


5, = 0.01 
42 
40 log ¥ + 1 = 0.02965X + 0.31756 4 
b 4 
P <0,01 





a JL 4 JL SS eS 
1 2 3 4 5 6 7 8 9 10 41 12,13 «14 Ss 16 17 18 19 20 
Miles 
Figure 3,--Total number of hornworm eggs laid on 25 
plants of tobacco in each of 48 fields from June 15 to 
August 6, 1964, plotted against distance from center 
of light-trap area, 
was a difference in the number of tobacco 
fields producing the overwintering brood of 
hornworms, In the Oxford area, diapausing 
hornworms are found in tobacco fields in August 
before the crop is harvested and in September 
on suckers that grow on the stalks after the 
leaves have been removed, Early destruction of 
these stalks for nematode and insect control 
has been a standard recommendation for many 
years (Metcalf 1909), Nevertheless, surveys in 
previous years have shown that about 40 per- 
cent of the tobacco fields in the Oxford area 
are left undisturbed long enough to produce 
some overwintering hornworms on suckers, 
The general survey made in the fall of 1961 
covered only part of the light-trap area, and 
the data are not adequate to determine whether 
or not there were any differences between the 
area covered by light traps and the area out- 
side. In 1962, there was a tendency for the 
number of stalk fields to increase from the 
center out to 14 miles, Fourteen percent of 
the fields remained inside the area as com- 
pared with 37 percent outside, There was evi- 
dence that farmers in the area had begun to 
