112 MISCELLANEOUS STUDIES 



Sebastopol; Morrison has taken the sexes at Stanford University on 

 December 16 (1910) ; Moznette of the Oregon station has taken the 

 migrants as late as the middle of November at Corvallis, Oregon. 

 Consequently, egg laying probably occurs from the middle of October 

 well into December in the various parts of California. Commissioner 

 Norton states: "The first eggs that I have seen were observed about 

 the fifteenth of October. However, they continue egg laying, in 

 favorable years, well along into November. ' ' 



The injury caused by this aphid is done entirely in the spring of 

 the year, before the summer migration, and consists in the curling of 

 the terminal leaves. The colonies are found usually in the leaves 

 surrounding a cluster of apples, and although most of the feeding is 

 on the leaves themselves oftentimes they feed upon the fruit. In 

 such a case the fruit (according to Weldon, ''Apple Growing in Cali- 

 fornia," Mon. Bull. Cal. Comm. Hort., p. 86, 1915) "is injured to 

 such an extent that it becomes stunted and not only fails to mature, 

 but is distorted so badly that' the variety may not be recognizable. ' ' 

 In Nevada County, Commissioner Norton reports: "The purple aphis 

 unless controlled lessens the apple crop from ten to fifteen per cent. ' ' 

 This is a higher percentage, undoubtedly, than is common throughout 

 the state, but it shows how serious the pest may be. 



130. Aphis marutae Oestlund 



Figures 293 to 299 

 Oestlund, Minn. Geol. Nat. Hist. Surv., vol. 14, p. 40, 1886 (orig. desc.). 



Eecords. Silybum marianum; Grossmont, San Diego County, April, 1916: 

 Centaurea melitensis; El Cajon, San Diego County, May, 1916. 



In April, 1916, the author observed a small aphid on milk thistle 

 near Grossmont, San Diego County, and later on tacalote in the 

 El Cajon Valley. It infested the smaller leaves, the leaf petioles, and 

 the base of the flowers. Large numbers of ants were in attendance, 

 but it was preyed upon extensively by the larvae and adults of Cocci- 

 nella California. A considerable number of adults of Lysiphlebus 

 testaceipes Cresson were reared from colonies of this aphid. Being 

 unknown to the author specimens were sent to J. J. Davis and E. 0. 

 Essig, both of whom determined the species to be Aphis marutae Oest- 

 lund. Inasmuch as Oestlund 's descriptions are the only ones avail- 

 able, a brief description is given below of specimens taken May 1, 

 1916, on Silybum marianum in San Diego County. 



