94 MISCELLANEOUS STUDIES 



This has been reported twice from pigweed or goosefoot in the 

 San Francisco Bay region, where Davidson states that it is very 

 common. The sexes occur in October. Davidson believes that there 

 is an alternate host, but as to what it might be, he is uncertain. The 

 author has never collected specimens, but has had access to material 

 taken by R. W. Doane on Chenopodium in Utah in August, 1916. 



111. Aphis avenae Fabr. 



Figures 191, 201, 202 



Fabricius, Ent. Syst, p. 736, 1775 (orig. desc.). 

 Clarke, Can. Ent., vol. 35, p. 254, 1903 . Nectarophora (list). 

 Davidson, Jour. Econ. Ent., vol. 3, p. 377, 1910. Siphocoryne (list). 

 Essig, Pom. Jour. Ent., vol. 3, p. 465, 1911. A. padi Linn. (list). 

 Essig, Pom. Jour. Ent., vol. 4, p. 790, 1912. A. maidis Fitch (desc). 

 Smith, Mon. Bull. Cal. Comm. Hort., vol. 3, p. 116, 1914 (list). 

 Davidson, Mon. Bull. Cal. Comm. Hort., vol. 6, p. 65, 1917 (note). 



Records. Graminaceae (various spp.) ; California, December to May (David- 

 son, Essig, Morrison, author) : PJialaris arundinacea; Stanford University, May 

 to July, 1915: Dracaena draco; Stanford University, June, 1915: Musa sapientum; 

 San Diego, March, 1916: Typha latifolia; (Davidson). 



This is an abundant species through the state, occurring during 

 the late winter and spring on grasses and grains, migrating to other 

 hosts as these become ripened and dried. 



The life history of this species, according to Davis (U. S. Dept. 

 Agr., Bull. Ill, April, 1914), is somewhat as follows: 



The spring colonies on grains and grasses originate from viviparous females 

 which passed the winter on the grains and grasses, or from spring migrants from 

 the apples or related fruits; i.e., the progeny of the aphids hatching from eggs 

 laid the previous fall on such trees. As the weather becomes cooler they seek the 

 lower parts or the roots of wheat and other plants of the grass family, and 

 here pass the winter as viviparous females; or the winged fall migrants from the 

 grain may seek such trees as the apple, where the true sexes are produced. 



Undoubtedly the most common method of wintering over in Cali- 

 fornia is on the roots and lower parts of the grains and grasses. This 

 species has never been collected on apples or other related trees in 

 this state, nor have the eggs ever been observed. During the early 

 spring it is found abundantly on the grains and small grasses, in 

 January and February in the southern part of the 'state, and during 

 April and May in the central part. As the grains ripen and the 

 stalks and leaves become hardened, it seems that the aphids migrate 

 to other varieties of grass which remain soft and green later, as 

 canary grass and reed grass and corn, or even to such hosts as the 



