VIVIPAROUS DEVELOPMENT IN SOUTH. 



47 



can not be sure of the species as they were not reared. Winged and 

 wingless viviparous females (figs. 7, 8) were, however, present at the 

 time the eggs were found, as were also those of both Aphis (Sipho- 

 coryne 1 ) and Macrosiphum. Mr. E. Dwight Sanderson obtained the 

 males and oviparous females of MacrosipTium granaria Buckt. in 

 Texas but only artificially in his rearing cages. Mr. K. A. Vickery, 

 of this bureau, found males, females, and eggs of Aphis maidi-radicis 

 Forbes at Salisbury, N. C. These instances mentioned above are 

 probably the most southerly points at which oviparous forms of 

 plant-lice have so 

 far been found in 

 the United States. 



In the Southern 

 States, wherever 

 there is sufficient 

 food, Toxoptera 

 apparently breeds 

 viviparously 

 throughout the 

 year; for this rea- 

 son the number of 

 generations here, 

 other things being 

 equal, should far 

 exceed that in the 

 Northern States. 

 As a matter of fact, 

 however, the dry, 

 hot, protracted 

 summers of the 

 Southwest are 

 probably disas- 

 trous to the species during the hot months, except perhaps in 

 secluded nooks, where there is a supply of succulent host plants. 



In northern Texas, as observed by Mr. Urbahns, during June of 

 1909, Toxoptera rapidly disappeared with the ripening of the grain 

 crops and the approach of hot weather. Winged forms migrated 

 with the breeze early in this month, and wingless forms soon perished 

 from extreme heat and a shortage of green food in the field. Obser- 

 vations clearly showed that it was almost impossible for the " green 

 bug" to live and reproduce in grain fields during the summer. While 



1 Probably Siphocoryne avense Fab. The use of the generic name Siphocoryne, as applied to this species, 

 is questionable, and is not at present followed by many, perhaps the major portion, of the students of the 

 Aphididge. According to Schouteden (Ent. Soc. Belgique, vol. 12, p. 217, 1906, Catalogue Aphides de 

 Belgique) it should be Aphis. Some of our best students, however, admit that this particular species, 

 avenx, is on the borderland between Siphocoryne and Aphis. 



Fig. 8. — The spring grain-aphis: Wingless viviparous female. Enlarged; 

 actual size, 2 mm. (Original.) 



