Efficacy of antibiotic treatment measured by quantitive real-time PCR. Number of endosymbionts present in the workers after the experimental period measured as pg DNA of the amount of the housekeeping gene tufB. Workers differed significantly in their content of Blochmannia (ANOVA: Welch- test of square-root transformed data: p < 0.001, F5,42 = 5.77). Groups differing significantly from each other in a Tamhane posthoc test are marked with different letters above the boxes. Diet categories marked with two letters are intermediate and not significantly different from the respective groups. Diets as in legend of Figure 1. Lines within boxes represent medians, and an outlier is indicated by a circle.