28 
Table 22. — Average number of worms per boll in planted cotton and in zoca, 1921 
Date Planted j 7noQ 
cotton Zoca 
June 18 i 0.14 0.44 
July 2 . ! .07 .63 
16 \ .67 1.47 
30 l 1.31 2.79 
Aug. 13 i 1.53 i 1.95 
27 ! 3.20 I 3.30 
Sept. 10 I 4.08 I 2.72 
26 ! 3.77 
Oct. 8 ! . _ 2.02 
FOOD PLANTS 
Experiments were conducted and observations made by A. C. 
Johnson on host plants other than cotton to determine the part these 
plants may be expected to play in the perpetuation of the pink boll- 
worm in the absence of cotton or its spread beyond extensive areas 
in which there is no cotton. Dry okra plants containing a large 
number of heavily infested pods were placed under a large screen 
cage in the winter of 1921-22. The following spring both okra and 
cotton were planted under this cage, the old stalks being allowed to 
remain. The cotton bloomed about the middle of June and the okra 
still later, but no infestation developed on either. 
On May 27, 1922, 200 okra pods were gathered from dry stalks 
that had been in the field all winter. An examination showed 3 
living larvae, 33 dead ones, and 1 pupal case. It is thus evident that 
under Laguna conditions the larva can survive the winter in okra 
pods on stalks in the field. In an okra pod, however, the larva is not 
so well protected against cold as in a cotton boll containing cotton. 
Other malvaceous plants growing in the Laguna district were like- 
wise studied with reference to their possible relation to the pink 
bollworm as host plants. A larva was found in a bloom of hollyhock 
(Althea rosea) as early as May 28 in 1922, and on June 7, 1921. Heavy 
infestation of hollyhock was never noted, and the larva was observed 
only in the bloom. 
Three wild malvaceous plants are rather common in the Laguna 
district. These are SpJiaeralcea cuspidata (Gray) , Sida Jiederacea Torr. , 
and Malva parviflora L. Quantities of these plants were collected 
repeatedly and placed in rearing cages, but no stages of the pink 
bollworm were ever found on them. In many cases these plants were 
collected immediately adjoining cotton fields. Larvae of the lepidop- 
teron Noctuelia rufofascialis Stephens were found in considerable num- 
bers in the seed pods of these plants. This larva attains practically 
the same size as the pink bollworm and it is found occasionally feeding 
on cotton, both in the blooms and in the bolls. The pods of these 
malvaceous plants are large enough to enable the pink bollworm to 
reach maturity in them. 
A few specimens of Hibiscus coulter i Harv. were found on the moun- 
tains near Tlahualilo, but they were not infested. 
RELATION OF ALTERNATIVE FOOD PLANTS OF THE PINK BOLLWORM TO NONCOTTON 
ZONES 
In the United States in the work of eradicating the pink bollworm 
the planting of cotton over extensive areas has been prohibited. 
This work appears to have been entirely successful in bringing about 
