r 
57 
less as a transition to the third type, which is pink or rose colored. 
The dorsal color pattern in a dark type of larva is shown in Plate VI, 
figure 4. 
DESCRIPTIONS OF INSTARS. 
Following are the detailed descriptions of the different stages of a 
generalized larva. ^ No reference is made to the color variations or to 
slight individual differences shown in the specimen at hand: 
Stage I. 
At exclusion from the egg the tubercle areas are pale and the cervical shield 
characteristically crescent-shaped, its posterior margin regularly convex, the anterior 
margin concave on each side and acutely produced medially. Shortly afterwards both 
become normal for instar I. 
Millimeters. 
Average length at hatching 1.5 
Average length before ecdysis 3. 8 
Average width of head ca^t 3 
'*Semi-looper." Body slender; pale translucent, yellowish in certain lights; 
greenish after feeding. Surface minutely hairy. Head much larger than the follow- 
ing segments, cordate; shining black, bearing many setae. Mouth parts, ocellar 
spots, and antennae pale. Cervical shield shining black, sometimes paler, bearing 
eight small tubercles arranged in two rows of four each; shape broad, peltate, the 
anterior and posterior margins emarginate or sinuate, the sides oblique. Anal shield 
dilute black, quadrate, emarginate behind; bearing eight small tubercles. Legs 
dusky, furnished with many stiff setae. Prolegs pale, their shields quadrate, dilute 
black, the latter being in reality the blackened area surrounding tubercle vii; the 
anal pair with an inverted V-shaped dusky marking on the lateral aspect; the two 
anterior pairs shorter than the others, first one-half as long as third and fourth and 
the second slightly shorter than the third and fourth. Spiracles inconspicuous, 
black. Body beneath pale, the ventral nerve ganglia showing through as single 
round orange spots on segments I to X. 
Tubercles minute, situated in large irregularly circular dusky areas which are 
absent in the larva directly after exclusion from the egg. Tubercles arranged as 
follows: 
Segment I : i-viii placed in two rows of four each above and in front of the spiracle. 
Segment II: Ten tubercles in a transverse row across the segment, the line curv- 
ing forward; i smallest, ii largest, twice the size of the next smaller and equal to v. 
A single tubercle aboye and behind the leg. 
Segment III: Arrangement the same; i smaller than i of preceding segment and vi 
farther back. 
Segment IV: i, ii, iii, and iv, circular, equal; seen from above i and ii form a trape- 
zoid; i slightly larger than ii; seen from the side iii, iv, and v form a triangle 
surrounding the spiracle, iv in the stigmatal stripe; vi absent; vii and viii minute, in a 
transverse row. 
Segment V: Arrangement the same; vii and viii in a triangular group on the 
venter, the first or outer of vii largest. 
« Combined from a series of twelve boll worms hatching from eggs laid by the 
same moth and reared under identical conditions. 
