Wheat Hour, in separate mixtures with eight different pH indicators, was fed to 10 species of small, stored-grain-infesting beetles. In the 575 individuals dissected, the pH of fore-, mid-, and hindgut, respectively, ranged as follows: Cryptolestes ferruginens, 4.6 to 5.2, 5.2 to 6.0, 4.6 to 5.2; C. turcicus, 3.6 to 4.6, 5.2 to 6.8, 4.6 to 5.2; Oryzaephilus mercator, 4.6 to 5.2, 5.2 to 6.8, 4.6 to 5.2; O. surinamensis, 5.2 to 6.0, 7.2 to 7.6, 3.6 to 5.2; Rhizopertha dominica, ca. 6.8, 5.2 to 7.2, 3.6 to 4.6; Sitophilus granarius, ca. 5.2, 6.8 to 8.4, 4.6 to 5.2; Tribolium castaneum, ca. 5.2, 7.2 to 7.6, 3.6 to 4.6; T. confusum, 4.6 to 5.2, 5.2 to 6.8, 3.6 to 4.6; Trogoderma parabile, 5.2 to 6.0, 7.2 to 8.0, 3.6 to 4.6; and T. versicolor, 5.2 to 6.8, ca. 6.8, 3.6 to 4.6.