10 BULLETIN 918, U. S. DEPARTMENT OF AGRICULTURE. 
LARVA. 
Newly-Hatched Lary.e. 
The newly-hatched larvae are creamy white, with dark-brown 
head and thoracic shield and long, prominent, dark setae showing 
very plainly. They are a little less than 1 mm. in length and grad- 
ually taper from the head, having thus a slight wedge-shaped appear- 
ance. In this stage the larvae are very active. Under laboratory 
conditions they are very restless and crawl rapidly from jelace to 
place before entering a square or boll. Many larvae continue crawl- 
ing around for 24 hours or more until they become so weakened that 
they are not able to cut their way into the squares or bolls. It was 
often observed that most of the larvae which succeeded in entering 
the food provided for them did so the day they were hatched. It is 
not known to what extent this wandering around takes place under 
natural conditions. Larvae are found crawling over the plants, but 
they always seem restless and ill at ease. This probably does not 
take place normally to any great degree, except in the case of larvae 
from eggs laid on other parts of the plant than the squares and bolls. 
Larvae Entering Bolls. 
The larvae do not seem to have any preference as to where the boll 
is entered. Sometimes a light netlike web is spun and the entrance 
is made underneath it. At other times the entrance is made with 
no protection whatever. The larvae cut the carpel away, throwing 
the fragments outside, very little if any being consumed. The time 
required for the larvae to enter may vary with the age of the boll, 
but it usually takes them from 20 to 40 minutes to become com- 
pletely hidden. If the boll is examined soon after they have entered, 
the holes are easily located by the surrounding frass, and although 
minute, can be seen with the naked eye. After 2 or 3 days the frass 
is blown away by the wind or removed by other agents and the 
holes close up, leaving only brownish spots which are hard to dif- 
ferentiate from other discolorations on the boll. Then they can 
only be detected by a trained eye, and the only way to be certain a 
boll is infested is to examine its interior. 
Lary.e After Entering Bolls. 
After the boll has been entered the larvae become glassy white, 
soft, and sluggish. They so closely resemble the watery lint at this 
stage that they would be very easily overlooked, except for their 
dark heads and thoracic shields, which show as black specks against 
the lint. 
There are three molts, completing four larval instars or stages. 
The first stage lasts about 2 days; the second and third, 3 to 4 days 
each; and the fourth, 4 to 5 days,; thus the larval development is 
