10 



BULLETIN 427, U. S. DEPARTMENT OF AGRICULTURE. 



THE FULL-GROWN LARVA. 



The full-grown larvae (fig. 7, left and right) are slightly fusiform in 

 shape, and plainly constricted at the segments. 



The head is dark brown, with the exception of the frons, which is 

 lighter in color. The cervical plate is black, with a pale narrow me- 

 dian line, and the thoracic 

 legs are black. The venter 

 and sides of the abdominal 

 segments are a waxy white 

 and the dorsum is gener- 

 ally a light pink, though in 

 some larvae there is enough 

 green present to give the 

 dorsum a very light green- 

 ish tinge . The spiracles are 

 small, dark, and inconspicu- 

 ous. There are about 10 

 to 14 small light hairs on 

 each segment, at the base 

 of each of which there is a 

 small black spot. There 

 are five pairs of prolegs, 

 and near the base of each, 

 on the outside, is a small black projection armed with three stout, 

 short, black hairs. The anal plate varies from a yellow to dusky 

 yellow in color. The full- 

 grown larva is from 9.5 to 

 11.5 mm. in length, and 

 when fully extended is 

 even slightly longer. At 

 the widest point the aver- 

 age is about 1.5 mm. in 

 width. 



As pupation approaches 

 the entire larva becomes 

 greenish in color, and 

 much shorter. 



THE PUPA. 



When first formed the 

 pupa (fig. 7, center; fig. 8) 

 is white, with green mark- 

 ings, but soon changes to deep uniform brown. In general form it 

 is spindle-shaped, being broadly rounded at the head, widest at the 

 thorax, and tapering evenly to the last abdominal segment. The 



Fig. 6. — Egg masses of the tuber moth on the surface of a 

 potato. Enlarged. (Original.) 



Fig. 7. — The potato tuber moth: Ventral view of larva at 

 left; dorsal view at right; pupa in middle. Larva much 

 enlarged; pupa still more enlarged. (Original.) 



