5 °° 
Journal of Agricultural Research 
Vol.V, No. w 
The mouth, pharynx, esophagus, and stomach have approximately the 
same form and relative positions as in the first instar. Owing to the 
fact that the blood of the host is green, the stomach content of the 
parasite at first takes on a greenish brown color which finally becomes 
a deep green, similar to the blood of the host, and later, at the end of the 
stage, this again becomes greenish brown. 
During the last two days of this stage the anal opening, the diameter of 
which nearly equals that of the body, slowly contracts, and violent con¬ 
tractions of the longitudinal muscles of the stomach, which cause it to 
shorten, slowly draw the caudal vesicle in through the contracting anal 
opening. The Malpighian vessels are also drawn in by the contraction 
of the stomach and are now two-thirds as long as the larva. After the 
caudal vesicle has been drawn completely within the body, the anal 
opening contracts still further, and the anus is formed. 
The tenidia of the tracheal system can be seen forming soon after the 
first molt. Those of the two main longitudinals and their anterior con¬ 
necting branches are first visible, and there are 11 branching centers on 
each longitudinal from which arise branches sending tracheae to all parts 
of the body, some even extending posteriorly into the caudal vesicle 
along the lateral walls and the stomach. Nine pairs of short, stublike 
branches are noticeable in the older larvae, arising near the bases of the 
anterior nine pairs of dorsal branches of the main longitudinals. In the 
still older larvae, those nearly ready to emerge, eight pairs of spiracles can 
be seen forming at the surface of the body, and these are connected with 
the first, and the third to ninth, inclusive, pairs of stublike branches 
previously mentioned, by tracheae destitute of air. These become filled 
with air when the larva molts at emergence and the spiracles are un¬ 
covered and function. The spiracles that connect with the second pair 
of stublike branches do not form during this stage. 
After the caudal vesicle has been drawn in, the larva is ready to emerge 
from its host. The mandibles of the third instar, which are now devel¬ 
oped and protrude, slowly cut and tear through the muscles and skin of 
the host as the larva presses its head against the body walls of the cater¬ 
pillar and moves them backward and forward. When a slit has been 
made of sufficient size the larva squeezes through the opening, molting 
the previously loosened skin as it emerges. During this process the 
caterpillar lies quietly as though paralyzed. About the time the parasites 
have nearly finished their cocoons, it usually revives enough to crawl 
away. 
Third instar (PI. L, fig. 7).—The third instar lasts from the emer¬ 
gence from the host until pupation, the time being approximately 2% 
days. 
The newly emerged larva is light green in color. It is covered with 
minute spines, with a number of short black spines somewhat irregularly 
