32 BULLETIN 885, U. S. DEPARTMENT OF AGRICULTURE. 
position and go through the same rotating movement on settling 
down again. On leaves bearing large numbers of spirals or on small 
leaves, as in the case of orange jessamine (CJialcas exotica), the larvae 
seem to show a tendency to settle down along the smaller veins of the 
leaf and parallel to them, but this position is lost, due to the rotation 
that takes place in the later larval instars just after molting. 
The duration of the first larval instar ranges from 7 to 16 days, at 
which time the first molt takes place. In a great many cases, 
especially out of doors, larvae that fail to molt before the sixteenth 
day fail to mature. The mortality in this instar, as is shown in both 
laboratory and field life-history work, is exceptionally high. Out of 
580 individuals that entered this stage of development 190, or about 
32 per cent, died. 
SECOND LARVAL INSTAR. 
As the insect molts from the first to the second larval instar (PL 
VIII, A), a whitened margin along the sides of the insect can be 
seen as much as two days before the actual molt takes place. The 
individual has a decidedly distended appearance, and there is a slight 
constriction (almost unnoticeable in the first molt) on the side of 
the body apparently at the junction of the thorax and abdomen. 
Just before molting there is also a decided bulging along the line 
of the thorax and abdomen forming a transverse ridge. The insect 
seems to burst the anterior latero-ventral margin of its skin by 
pushing forward, and flows forth much like a drop of cream-colored 
viscous liquid. It begins at once to flatten out, being more ovate in 
shape than in the previous instar and quite disklike. This flattening 
out causes the skin to tear farther and farther back until at last the 
insect is free, with the skin attached to the dorsal spines. At this 
time the insect, both to free itself from its cast skin and to insert its 
rostral setae, goes through some rather violent movements. It begins 
to rotate, describing an arc of from 45 to 180 degrees, and at the end 
of this movement it may raise the posterior portion of the body until 
it is almost over the anterior portion, so that as viewed from the 
side the insect would have a crescentic appearance. The insect may 
stay in this position as long as 5 minutes. Then again the posterior 
end of the body may be raised only slightly, and this movement be 
alternated with a "cupping up" movement, the insect assuming 
the shape of a person's hand when it grasps a pen. Or again at the 
end of each rotation the insect may merely rest for from 30 to 70 
seconds. The time for normal procedure seems to be: Time to cast 
skin, 7 to 10 minutes; rotation with miscellaneous movements, 15 
to 30 minutes. The entire time of molting, therefore, is about 40 
minutes for the first molt. Several times it has been observed that 
insects started to molt and did not complete the operation until 24 
hours later. 
