Fig. 4. Conditioned responses from two different groups of animals that collected different unscented sucrose concentrations at the training feeder (either 0.5 mol l^-1 or 1.8 mol l^-1) prior to trophallaxis. Once in the arena, all the animals received scented (5 µl l^-1) 1.8 mol l^-1 sucrose solution during trophallaxis. Data are presented for the first (%PE₁, white bars), the second (%PE₂, grey bars) and the third test (%PE₃, black bars). Animals were tested 21, 27 and 46 hfollowing trophallaxis in a cumulative fashion. Asterisks indicate statistical differences among tests (G-test, ^***P<0.001). The number of animals is given in parentheses. Differences in the sample size within each group are due to differences in mortality and US responsiveness prior to the tests.