Figure 1.
Preference scores for NaCl vs. Pure substrate as the NaCl concentration at test is increased, as a function of NaCl concentration in the food on which the larvae were reared (from top to bottom, food with no added salt, food containing 0.25 M NACl, 0.275 M NaCl, 0.3 M NaCl, or 0.43 M NaCl).
Each boxplot represents ten trials, and * denotes a significant difference from zero (the calculated confidence interval of the sample mean with (0.05/8) does not include 0). The blue line indicates the lowest NaCl level for which significant aversion occurs, and the start of the shaded area the highest significantly attractive level. The lowest aversive level increases when the NaCl concentration in the food is increased.
Figure 2.
Larvae reared on 0.2 M, 0.25 M or 0.3 M NaCl food tested: (left) for untrained preference between Pure (white) and 0.275 M NaCl (shaded) substrate; (right) for odour preference after associative training with a Pure or 0.275 M NaCl substrate, tested on Pure.
* denotes a significant difference from zero (the calculated confidence interval of the sample mean with (0.05/3) does not include 0, see text). For larvae reared on 0.25 M food (dark grey), the 0.275 M substrate is aversive but the odour associated with it becomes more attractive.
Figure 3.
Larvae reared on 0.2 M (light grey) and 0.3 M (dark grey) tested: (left) for untrained preference between Pure (white) and NaCl (shaded) substrate at a concentration 0.025 higher than their food, i.e., 0.225 M and 0.325 M respectively; (right) for odour preference after associative training with the corresponding substrates, tested on Pure.
* denotes a significant difference from zero (the calculated confidence interval of the sample mean with (0.05/2) does not include 0, see text). In both cases an aversive substrate has a positive reinforcement effect.