6 BULLETIN 438, U, S. DEPAETMENT 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 (iSg. 1, c) measures 12 mm. (0.5 inch) in length 

 and 1 .6 mm. in width. The head is light green, dotted antero-dorsaUy 

 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-f rontaUy 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 Jarvse 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; PI. I, fig. 4) is cylindrical; shghtly 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 fight greenish and if kept dry re- 

 mains a straw color, but if moistened, as 

 it usually is when spun in the soil, it soon 

 ^'""-■J-"^"^! ^'fJn- ?r°°' darkens, becommg a dark brown. Some 



Much enlarged. (Origmal.) ' o 



larvae spin a quantity of loose, red-brown 

 silk about the outside before spinning the fight-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 fies 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 sUghtly 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 larvae 

 spin their cocoons within an inch of the surface, and during the long 

 dry summers of Cafifomia and Washington this top inch of soil is 



