A SYNOPSIS OF THE APHIDIDAE 79 



27. Genus Phorodon Passerini 

 Passerini, Gli Afidi, 1860. Type P. humuli Schr. 



No attempt has been made to formulate a key to the California 

 species of this genus, owing to the fact that the author has specimens 

 of but one species, and that the description of the other is quite inade- 

 quate. Four species have been reported from this state, two of which 

 prove to be species of other genera and one of which is very doubtful. 

 Phorodon carduinum (Walker) as reported by Davidson, is Myzus 

 braggi Gillette. Phorodon galeopsidis (Kaltenbach), also reported by 

 Davidson, is Rhopalosiphum hippophoaes Koch. There is much 

 diversity of opinion concerning the specific determination of these 

 species and of Myzus elaeagni "Del Guercio. One might refer to Gil- 

 lette 's paper on Rhopalosiphum hippophaaes Koch and Myzus braggii 

 Gillette. Davis writes that he is not prepared to be quoted. Davidson 

 lists P. galeopsidis and R. hippophoaes as synonyms. He states that 

 his specimens listed as P. carduinum Walker were determined by 

 Monell, but that Van der Goot is doubtful, while he himself believes 

 them to be M. braggii Gillette. He has been followed in so listing 

 them. This then leaves but two species reported from California. 



98. Phorodon humuli (Schrank) 

 Figures 115 to 118 



Schrank, Fauna Boica, vol. 2, p. 110, 1801-02. Aphis (orig. desc.). 



Clarke, Can. Ent., vol. 35, p. 252, 1903 (list). 



Clarke, Calif. Agri. Exp. Sta., Bull. 160, 1904 (econ.). 



Parker, U. S. Dept. Agri., Bull. Ill, 1913 (econ.). 



Vosler, Mon. Bull., Cal. Comm. Hort., vol. 2, p. 668, 1913 (list). 



Records. Humulus spp. ; Berkeley (Clarke); Placer County' (Vosler) ; Berke- 

 ley, July to September, 1915: Prunus domestica; Berkeley, March to April, 1915 

 (Essig, Shinji) ; (Parker). 



This is the common hop plant louse found throughout the central 

 part of the state. During the summer it is common on hops, but in 

 the fall the sexupara migrate to plum, where the eggs are laid. These 

 eggs hatch the following spring into stem mothers which feed on the 

 opening buds of plum. During later generations, probably about the 

 third or fourth, alate fundatrigeniae appear, which leave the plum 

 and migrate to hop. Here the summer generations are produced until 

 well into the fall. Parker states that the normal life cycle is as just 

 stated, but that it is also possible, and it occasionally occurs, that this 



