144 THE MONTANA EXPERIMENT STATION 



DETAILED DESCRIPTION OF THE LARVA. 



Head with ground color sordid white with a yellowish tinge; with 

 dark brown markings as follows: a dark line in a transverse de- 

 pression on lower side of clypeus directly above which is a row of 

 dots marking the positions of setae; dots on the sides of thi head, 

 behind and above, grouped and confluent, leaving open spaces; a 

 subquadrate patch on each side of the clypeus following the converg- 

 mg sutures, not joining above but diverging again, more or less 

 narrowed as they pass backward; a spot just back of the ocelli. 

 Antennae translucent, whitish with terminal joint brown. Mandi- 

 bles tipped with black. Body with prevailing cast distinctly dark 

 above. A sordid white, more or less broken dorsal line extending 

 from the head to the anal shield with marked subdorsal lines of yel- 

 lowish brown, which, with the dorsal line, give the appearance of a 

 well marked broad stripe down the dorsum ; an indistinct sordid 

 white lateral line; the entire venter, from stigmata down, pale trans- 

 lucent brownish, finely mottled with sordid white. Sparsely but 

 regularly scattered over the body are glossy spots or low tubercles, 

 each bearing a fine short hair. Under the naked eye the hairs are 

 scarcely -visible. Length, 28 mm. As the caterpillars increase m 

 size but little change of general appearance is to be noted. The 

 largest specimens, when full fed, measure 55 mm. in length. 



PUPATION 



When full grown the larva constructs a vertical oval cell in the 

 soil about two or three inches below the surface, using its head as a 

 spatula, smoothing the walls and giving them a regular shape. After 

 remaining in this sell for about six days the skin is molted off and the 

 insect appeas in the pupa state. The pupa is brown in color, much 

 shorter than the caterpiller, and the head end is pointed upward. In 

 our experience as given in the seasonal history above, the duration 

 of the pupa stage is about eight weeks, or about nine weeks including 

 tthe six days of preparation for pupation. 



THE ADULT MOTH 



■« 



(See figure accompanying.) Detailed descriptions of the three 

 species mentioned in this paper are given elsewhre in technical lit- 



