INSECTS INJURIOUS TO BEETS AND SPINACH 



331 



" No sexual generation of this aphis has as yet been discovered 

 nd no eggs have been seen, viviparous reproduction continuing 

 throughout the year except when the cold of the winter tempora- 

 rily suspends the physiological activities of the species. The 



FIG. 237- The beet-aphis (Pemphigus betas Doane) : a, winged female; 6, 

 wingless female; c, antenna of winged female. (After Doane.) 



winged females, appearing from time to time during the summer 

 and fall, serve to distribute the species generally, new colonies 

 being started wherever these females find lodgment and food. In 

 districts liable to injury by this insect it seems inadvisable that 

 beets should be the first crop on new land, or that ground should 



be continued in beets or in any other 

 root-crop after the pest has made its 

 appearance in the field." 



Another plant-louse, called the beet 

 root-aphis *, proved injurious to sugar- 

 beets in Colorado in 1903. They were 

 found " quite generally distributed in 

 the beet-fields in the vicinity of 

 Rockyford and attacking the roots of 

 many weeds." What seemed to be this 

 species was very abundant upon the 

 roots of the common garden purslane, 

 to which it was very injurious. Near 



o 



FIG. 238. Beet root-aphis 

 (Tychea brevicornis Hart): 

 a, aphis; b, antenna; c, 

 tarsus all greatly enlarged. 

 (After Garman). 



* Tychea brevicornis Hart. 



