Fig. 5. Experiments 3 and 4, showing the photoresponse of individually assayed larvae, tested on either PURE agarose or on agarose plates containing gustatory stimuli. (A) Percentage of CS-F larvae located in a covered ('dark') quadrant in Experiment 3. Animals were observed every 10 s for 5 min in an X-plate photoresponse assay. The 50% line indicates random distribution. Animals were tested on either fructose (FRU; 1 mol l^-1), quinine hemisulfate (QUI; 0.2%), sucrose (SUC; 1 mol l^-1), or NaCl (2 mol l^-1). (B) For each animal, a PREF value was calculated; positive values indicate dark preference and negative values, light preference. The box plot represents the median as the middle line and 10 and 90, and 25 and 75% quantiles as whiskers and box boundaries, respectively. No significant difference between the PREF values was found. Sample sizes were N=150, 150, 142, 146, and 144 for FRU, QUI, SUC, NaCl and PURE, respectively. (C) Experiment 4 is a repetition of Experiment 3, but using animals from the CS-W wild-type strain and employing the down-sized X-plate assay. PREF values were tested on either PURE agarose or on agarose plates, containing FRU (2 mol l^-1) or NaCl (4 mol l^-1). Sample sizes from left to right, N=88, 88, 72.