NUMBER OF 
log y = 2.5104 - 0.2698 x 
&= .O147 
p< .001 
Figure 3.--Regression of number of marked P. sexta males 
recaptured in light traps on days after release, 1961. 
EFFECT OF TRAPS ON HORNWORM NUMBERS 
It was apparent from the 1961 data that hornworm moths were strong fliers 
and capable of moving 3 or 4 miles in a single night. Thus, if any control 
method is applied to a small area, this area will almost certainly be flooded 
by moths flying in from outside. The size of the area required for a control 
experiment can be estimated from the 1961 trap data, provided some allowance is 
made for the movement of moths over a larger and larger area as they dispersed 
from a central point. To correct for the distance factor, we assumed that moths 
dispersed at random and the effective range of all traps was the same and 
circular. If the diameter of this circle is "d" and the distance of a trap from 
the point of release is "r," then the catch of the trap should be approximately 
proportional to _d_. Since "d" and "2m" are constants, an approximate 
2ar 
correction can be obtained by multiplying the catch by "r." 
= 2 — 
