120 Wisconsin Academy of Sciences^ Arts^ and Letters. 
oi'obanches, Macrosiphum Lichtenstein, 1884. La Flore des Aphl- 
dens, p. 37. No description. 
Orohanche sp. 
orthocai'pus, Macrosiphum Davidson, 1909. Jour. Econ. Ent. II, 
p. 304, 
Orthocarpus sp. 
osmaroniae, Illinoia Wilson, 1912. ‘Can. Ent. XLIV, p. 153. 
Osmaronia cerasiformis. 
ovata-oblongus, Pemphigus Kessler, 1881. Ber. Ver. Naturkunde 
Kassel, XXVIII, p. 61, fig. 
Populus nigra, P. pyramidalis. 
oxalis, Aphis Macchiati, 1883. Bui. Ent. Soc. Ital., XV, p. 255. 
Oxalis corniculata. 
oxybaphi, Aphis Oestlund, 1887. Aphididae of Minnesota, p. 62. 
Oxyhaphus angustifolius, 0. linearis, 0. nyctagineus. 
oxyacanthae, Aphis Koch, 1854. Die Pfianzenlause Aphiden, p. 
55, fig. 
Pyrus communis. 
oxycauthae, Myzus (Schrank), 1801. Fauna Boica, II, p. 116. 
Aphis. 
Crataegus oxycantha, Prunus chamaecerasus, Pyrus communis, P. 
malus. 
paczoskii, Acyrthosiphon Mordwilko, as a var. of A. gossypii Mord- 
wilko, which see. 
padi, Aphis Linnaeus, 1758. Edition 10, Systema Naturae, p. 451. 
Alopecurus pratensis, Crataegus oxyacantha, Prunus padus, Pyrus 
aucuparia, P. germanica, P. malus. 
padi, Lachnus Hartig, 1841. Zeit. Ent. (Germar), III, p. 368. 
Alopecurus pratensis. Prunus padus. 
palens, Aphis Walker, 1852. List. Homop. Insects Brit. Museum, 
part 4, p. 1043. 
Food plant not given. 
paliuri, Aphis Lichtenstein, 1884. La Flore des Aphidens, p. 37. 
No description. 
Paliruim sp. 
