Fig. 8. Neither N2 (grey lines) nor CB4856 (black lines) migrates to their cultivation temperature regardless of food availability. Because starved worms rapidly migrate off unseeded thermal preference gels, the duration of these assays was reduced to 1 h, resulting in the observation of slightly higher estimates of mean thermal preference (see text). Worms raised for two generations at 14°C, 20°C or 24°C were assayed for thermal preference with OP50 present on the thermal gel (solid line) or without food (broken line). Mean thermal preferences are based on 3–5 replicates with a mean of 181 individuals per replicate for a total of 7059 individuals. Values are least square means ± 2 s.e.m.