Fig. 1. Basal and inducible thermotolerance in the Oregon R (OR25), T25 and T32 strains of Drosophila melanogaster. Batches of 4-day-old adults were exposed to the indicated temperatures for 30min either with or without a heat pretreatment (PT) as indicated. Means are plotted ±1 S.E.M. (N=2–5), which the plotted points often obscure. All axes use identical scales to facilitate comparison. (A) Thermotolerance in flies without pretreatment. (B–D) Thermotolerance of the three strains with and without a pretreatment. In B–D, without-pretreatment data are replotted from A.