180 Wisconsin Academy of Sciences, Arts, and Letters. 
xanthii, Siphocoryne Oestlund, 1886. Aphididae of Minnesota, p. 
36. 
Xanthium canadense. 
xanthomelas, Chaltophorus Koch, 1854. Die Pflanzenlause 
Aphiden, p. 1, fig. 
Lycium europaeum. 
xylostei, Prociphilus (DeGeer), 1773. Mems. des Insects, III, p. 
96, fig. Aphis. 
Lonicera xylosteum, Picea sp. 
xylostei, Siphocoryne (Schrank), 1801. Fauna Boica, II, p. 107. 
Aphis. 
Conium maculatum, Lonicera caprifolium, L. japonica, L. peri- 
clemunum, L. xylosteum. 
yuccae, Aphis Cowen, 1895. Hemiptera of Colorado, p. 122. 
Yucca glauca. 
yuccae, Aphis Lichtenstein, 1884. La Flore des Aphidens, p. 55. 
No description. 
Yucca sp. 
yuccicola. Aphis Williams, 1911. Aphididae of Nebraska, p. 61. 
Yucca glauca. 
zeae. Aphis Bonafous, 1835. Ann. Soc. Ent. France, IV, p. 658. 
Zea mays. 
zeae. Aphis Curtis, 1842. Gardners Chronicle, II, p. i, fig. 
Zea mays. 
zehntneri, Ceratopemphigus Schouteden, 1905. Spolia zeylanica, 
II, p. 187, fig. 
Pistacia atlantica. 
