
Y = 89.47X + 94.86 | 
900 + sp = 1.598 7 
| 
P <0.01 





4 4 = 
a 
4 6 8 10 

RYE 
Number of Virgin Females 
Figure 7,--Number of male P, sexta moths caught in 
light traps when virgin females were held in small 
cages at trap, Females were rotated between trap 
locations so that each location received all treat- 
ments, 

Table 2.--Comparative catches of P. sexta 
in light traps with and without virgin 
females held in a small cage inside 
trap. (4 replications.) 
pete Average moths per 
Virgin trap per day 
females 

1 Differences in catches of both males and 
females are significant at 5-percent level 
by F test. 
two will triple it, etc. However, in a later ex- 
periment the number of virgins was increased 
to 30, but the catch was increased only 25 per- 
cent, 
In the large light-trap experiment, the com- 
paratively high reductionin males did not affect 
the fertility of the females, However, the very 
large increase in male catches when virgin 
females (or an equivalent amount of attractant) 
are added might well do so, particularly if the 
males caught can be sterilized and released, 
In conclusion it may be said that, although 
further work will be necessary to test these 
methods in other localities and to determine 
more exactly the contribution of different 
factors to the total reductionin numbers, there 
is no question that hornworm populations and 
insecticide usage on tobacco can be much re- 
duced, These results also suggest that, although 
any one population-control measure may not be 
enough by itself, the use of two control measures 
may be highly effective and much cheaper than 
insecticides, 
SUMMARY 
Previous tests of light traps for the control 
of various insects have generally shown these 
devices to be ineffective except at short dis- 
tances, At Oxford, N.C., in 1961, marking and 
recapture data indicated that numbers of horn- 
worms (Protoparce sexta (Johannson) and P, 
quinquemaculata (Haworth)) might be reduced 
by traps if the area were large enough, In 
1962, a test was Set up with three traps per 
square mile in a circular area 12 miles in 
diameter, In the first year, the number of 
females per trap was reduced more than 50 
percent and males more than 75 percent atthe 
center of the area as compared with 6 miles 
outside, In 1963 and 1964, interpretation ofthe 
results was complicated by an increase in 
cultural control in the area, The reduction in 
moth populations was greater in these years, 
and the numbers of eggs laid on tobacco, 
damage to the crop, and insecticide usage 
decreased from 70 to 90 percent, Populations 
of other insects were also affected, 
In| experiments using variable numbers of 
virgin female hornworms in small cages near 
light traps, each female up to 10 caused the 
catch of males to increase by an amount ap- 
proximately equal to the catch of males in the 
light traps alone, 
