Vol. 1] Essig. — Aphididae of California 341 



creek milkweed, Asclepias speciosa Torr. At Niles an oleander 

 tree was seriously infested July 28, 1916. It was also taken on 

 woolly milkweed, A. vestita H. & A., at Visalia, California, July 

 27, 1916, by W. P. Baird. This is without doubt the common 

 milkweed species described by Montell a.s Aphis lutescens and 

 occurs generally throughout the state. 



Aphis oenotherae Oestlund. A small dark green, somewhat 

 pulverulent species occurring in large numbers among the buds 

 and on the flower heads of the evening primrose. Taken on 

 Oenothera biennis Linn, on the campus, June 7, 1916, and on 

 the common evening primrose, 0. grandifiora Ait., and on Epi- 

 lohium adenocaulon occidentale Trelease in Golden Gate Park. 

 San Francisco, California, May 25, 1916. 



Aphis persicae-niger Smith. A small shiny black species often 

 abundant on the tender shoots of peach trees. During the past 

 few years it has been received from a number of localities as 

 follows: Peach, Berkeley, California, April 29, 1915; peach, 

 Dinuba. California, April 30, 1915; peach, Yuba City, California. 

 March 25, 1916 (II. P. Stabler) ; peach, Fresno, California. ]\Iay 

 10, 1916; peach, Ventura, California. July 17, 1916 (S. H. 

 Essig). In the latter case the infestation was severe and much 

 of the fruit was also infested. This insect, though distributed 

 throughout much of the state, has never become a serious orchard 

 pest and only abundant on rare occasions. 



Aphis pomi DeGeer. This small green and black aphid is a 

 serious pest to a number of valuable ornamental trees in this 

 section, notably the English hawthorn, Crataegus oxijacantha 

 Linn. At Berkeley it has also been taken on the following : 

 Crataegus ^pp., laurestinus, Viburnum tinus Linn., tarata, Pittos- 

 porum eugenioides A. Cunn., tawhiwhi, P. tenuifolium Gaertn., 

 Cotoneaster franchetii Bois., apple and pear, as well as a number 

 of other undetermined plants. The foliage is covered with 

 honey-dew and soon collects dust or becomes covered with the 

 black smut fungus so as to assume a most undesirable appearance. 



Aphis rumicis Linn. A dull black species occurring in dense 

 colonies and generally confused with another species which I 

 am calling Aphis hederae Kalt. What, according to Davis, 

 is true A. rumicis has been taken at Berkeley, California, on the 

 Western dock, Rumex occidentalis Wats, April 13, 1916, and on 

 other species of Rumex and on the common garden poppy, 

 Papaver, sp., Jmie 15, 1916. 



