Sugar Beet Root-louse 



it crawls in among the expanding leaves and begins to feed upon the 

 upper surface of one close to the midrib. This feeding causes a depression 

 to form and the leaf to turn light in color (Fig. 1-A, Plate II). 



In the course of a few days this depression has become a swelling on 

 the under side of the leaf (Fig. 4, Plate II), which is now entirely closed 

 on the upper side (Fig. 3, Plate II). In this gall, as the swelling is called, 

 the little louse is securely protected from inclement weather and the 

 sharp-eyed birds as they flit among the branches. Both the gall and the 

 louse increase in size for some time, until the former appears as in Figure 

 5, Plate II, and the louse, which is called a stem-mother, as shown in 

 Figure 6, Plate II. 



This rotund stem-mother gives birth to several living young daily 

 during the next month or six weeks. If opened about the middle of 

 June the gall will be found to contain many pale lice all surrounded by 

 a whitish substance. This waxy material is secreted by glands and 

 escapes through what are called wax-pores, which are arranged in rows 

 across the body of the insect. These appear as light, round spots on the 

 back. (Fig. 6, Plate II). 



The young of the stem-mother do not resemble her in form, being 

 slender of body and at first wingless. As they grow older wing pads 

 appear on their shoulders. After shedding their skins several times, 

 growing darker with every succeeding molt, the last larval skin is shed 

 and a delicately winged louse (Fig. 7, Plate II) emerges. The antenna 

 of this winged louse is shown in Figure 8, Plate II. 



About the time the first winged lice appear the mouth of the gall 

 begins to open. Through this opening the winged lice escape and fly 

 or are blown by the wind far and wide among the beet fields, where they 

 settle on the beets and deposit their young, which immediately descend 

 to the ground and take up their abode on the beet roots. All the young 

 of the winged migrants from the cottonwood trees are wingless and when 

 full grown appear as shown in Figure 9, Plate II. 



The antenna of the wingless lice which are found on the beet roots 

 is shown in Figures 1 1 and 12, Plate II. 



These wingless lice give birth to still more wingless lice. This goes 

 on until several generations and hundreds of lice have been produced on 

 the beets. Then with the return of fall some of the lice on the beet roots 

 develop wing pads like those of the young of the stem-mother in the gall. 

 After acquiring wings these lice are known as the fall migrants. 



These migrants return to the narrow-leaf cottonwoods and there 

 deposit their young. Thus we have followed the lice from the galls on 

 the cottonwood trees to the beet fields and back again to the cottonwoods. 



Not all of the lice become winged in the fall, however. Some wing- 

 less ones remain over the winter in the soil, where they hibernate in 

 earth-worm burrows and other openings. Thus we see that nature has 

 provided two means of carrying the beet root-lice over the winter: the 

 hibernating lice in the soil, and the eggs in the crevices of the cotton- 

 wood bark. 



58 



