6 BULLETIN 438, U. S. DEPARTMENT OF AGRICULTURE. 
a characteristic curled position, and when the larva is disturbed this 
posterior curled part is thrown up in a threatening manner. 
The full grown larva (fig. 1, c) measures 12 mm. (0.5 inch) in length 
and 1.6 mm.inwidth. The head is light green, dotted antero-dorsally 
with small brown dots. Upon closer examination these dots are seen 
to be divided into two or three parts which fit closely together. The 
eyes are black; the mouth parts dark brown, and the clypeus light 
brown with a narrow inverted V-shaped band of green between it and 
the dotted area, which latter extends from the eyes back to the inser- 
tion of the head into the thorax and is divided dorso-frontally by a nar- 
row green line. Ordinarily the larva when full grown drops to the 
ground, but some have been noticed crawling about the trunks of the 
trees as though crawling to the soil. This is unusual, however, and 
probably occurs with those larve that happen to have been feeding 
near the main trunk. Just before the larva is ready to drop to the 
ground for ‘‘cocooning,”’ the caudal segments turn yellowish. 
THE COCOON AND PUPA. 
The cocoon (fig. 2; Pl. I, fig. 4) is cylindrical, slightly constricted 
at the middle, rounded at the ends and somewhat larger at one end 
than at the other. It is closely woven of 
fine silk, smooth inside and roughened or 
with a pebbled appearance, due to the ad- 
herence of small bits of soil, outside. It is 
at first light greenish and if kept dry re- 
mains a straw color, but if moistened, as 
it usually is when spun in the soil, it soon 
darkens, becoming a dark brown. Some 
larve spin a quantity of loose, red-brown 
silk about the outside before spinning the light-green cocoon, especially 
if the cocoon happens to be spun among old leaves in the soil, and 
an occasional cocoon is found which is entirely of this red-brown 
color. The larva lies with its head in the small end of the cocoon, 
and the posterior part of the body curled up in the larger end. In 
Washington the average length of 20 cocoons was 5.7 mm. and the 
average Maximum width 3 mm. In California the measurements 
of both width and length were slightly in excess of this. 
The habit of cocooning in the soil seems to be for protection rather 
than for the effect of moisture. Cocoons spun in dry glass vials in 
May, 1914, gave adults in April, 1915, though they had been kept 
perfectly dry during the intervening 11 months. The cocoon is 
closely spun and very tough and undoubtedly prevents the evapora- 
tion of any moisture from the inclosed larva. Most of the larve 
spin their cocoons within an inch of the surface, and during the long 
dry summers of California and Washington this top inch of soil is 
Fig. 2.—Pear leaf-worm: Cocoon. 
Much enlarged. (Original.) 
