According to Ashmead (1896) and others, the wasps belonging to the genus Polistes usually feed their young chewed-up fragments of lepidopterous larvae. However, Riley (1873) mentions P. rubiginosus Lept. as one of the natural enemies of the Colorado potato beetle, Leptinotarsa decemlineata Say, whose larvae it carries to its nest. A varied diet is therefore to be expected in these wasps. Nevertheless, I was very much surprised when I came across a rubiginosus engaged in a violent struggle with a large cicada (identified as Tibicen auletes Germ. by Mr. William T. Davis), at Ranken, Missouri, on July 19, 1932.