374 
Journal of Agricultural Research 
Vol. XI, No. 8 
border and mandibles are dark brown to nearly black, and the posterior 
part of the head clear light amber. The anterior and lateral borders of 
the first body segment are of a shining, yellowish brown, and the pos¬ 
terior half velvety-brown; the remaining segments are creamy-white 
throughout. The dorsal and ventral surfaces of abdominal segments 
are tuberculate, the minute dorsal tubercles being arranged in four 
irregular rows, forming two irregular oval rings, one within the other. 
The last segment bears on its ventral surface a small group of amber- 
colored, chitinous spines. 
Mr. F. C. Craighead, of the Bureau of Entomology, who has especially 
studied the classification of the larvae of the Cerambycidae, gives the fol¬ 
lowing characters for distinguishing the larvae of Ptychodes trUineatus 
from others of that family: 
Sides of head converging posteriorly; dorsal surface of prothorax vellured on pos¬ 
terior half; dorsal and ventral surfaces of abdominal segments tuberculate, tubercles 
on dorsal surface arranged in four irregular rows. 
These characters will distinguish larvae of the subfamily Lamiinae, to 
which Ptychodes trUineatus belongs, from those of the other subfamilies. 
The presence of a small group of chitinous spines, on the ventral surface 
of the last abdominal segment, distinguishes the larva of the three-lined 
fig-tree borer from that of other species of the genus Ptychodes. 
molting and growth 
The number of instars, or substages in the growth of the larva of the 
three-lined fig-tree borer, is variable and the occurrence of the molts 
irrregular. A little more than half the specimens under observation 
molted only five or six times before transforming to the pupa, about one- 
fourth of them made the transformation after the eighth molt, and the 
remaining fourth after the fourth, seventh, ninth, or tenth molts. It is 
only rarely that as many as io molts occur in the larva. The insect will 
sometimes molt twice in close succession after being cut or otherwise 
injured, the extra molting being apparently a protective measure in such 
cases. In molting, the head cast splits slightly along the median ventral 
line, separates from the body integument, and is slipped off whole. The 
skin is slowly pushed back over the tip of the abdomen. 
There is also a wide variation in the duration of the larval instars. 
Each of the first three instars may be completed in anywhere from 3 
days to about 40 days, while each of the succeeding ones requires from 
about one week, as a minimum, to between 50 to 60 days, as a maximum, 
for those specimens which complete their growth in a single summer. 
With larvae which live through the winter from one season to the next, 
the later stages of growth will be much longer, requiring 5 or 6 months. 
The average duration of the different substages in the growth of the 
larva was as follows: Instar I, 8 days; II, 9 days; III, 12 days; IV, 16 
days; V, 23 days; VI, 26 days; VII, 38 days for those specimens not 
passing and 5 months for those passing the winter in the larval stage; 
