PINK BOLLWORM OF COTTON IN MEXICO. 47 
taken by the nymphs and adults of three species of small undeter- 
mined Hemiptera is evidently very high. The attacks on the 
small pink bollworm larvae from these predators are so important 
that daily examinations of all food placed in the breeding cages was 
absolutely necessary. Often one small nymph would destroy the 
larvae from a large number of eggs during the night. 
The larvae of a lace- wing, Ghrysopa rufilabris Burm., attacks 
the newly hatched pink bollworm and also the larger larvae in the 
flowers. 
Only very rarely is a dead larva found inside a boll. The feeding 
habits within the green boll greatly reduce the chances of attack by 
parasites and predators during this period. When the exit holes 
are cut, or the boll begins to open, or when the larvae are migrating 
to the ground, they are exposed to these enemies for a short time. 
This short period of exposure may account for the very few parasites 
found. Only three species and one specimen of each were found 
attacking the larvae. They were the Hymenoptera Habrobracon 
sp., Parisierola emigrata Rohwer, and a small dipteron, Tortri- 
ciopliaga tortricis Coquillett. The scarcity of these parasites during 
the two years proves very conclusively that no relief can be hoped 
for from this source. 
The pupae of the pink bollworm in Mexico were not attacked by 
parasites, so far as our observations show. 
The small chalcid TricJiogramma minutum Riley may prove bene- 
ficial in parasitizing the eggs of the pink bollworm, but it was not 
observed attacking the eggs until late in the season, and then only 
very rarely. 
An outbreak of mites, Pediculoides ventricosus Newport, occurred 
on the hibernating larvae in the laboratory in 1918. Steps were 
taken immediately to check them by burning all infested material. 
To what extent these mites occur in the seed houses was not deter- 
mined. 
REPRESSION. 
FUMIGATION OF SEED. 
From the known instances in which infestations have occurred 
from larvae planted in the seed there can be no doubt of the danger 
of planting infested seed. Several methods of killing the larvae in 
the seed have been used in Egypt and other places (10), but all 
fall into three classes: Immersion of the seed in some substance to 
kill the larvae, treatment with heat, or fumigation with poisonous 
gases. Immersion of seed in liquids is obviously out of the question 
where tons of seed are used for planting on a plantation. In Egypt 
larvae can be killed by exposing them to the heat of the sun. Pre- 
liminary experiments showed that the temperature in Mexico during 
the planting season was not high enough to kill the larvae and that 
