In all experiments except those for RU486 calibration, we used our laboratory stock of outbred wild type Drosophila melanogaster, Dahomey, which has been cured of Wolbachia by tetracycline treatment 1 . Flies were maintained in large population cages with overlapping generations at 25 °C with a 12 h: 12 h light: dark cycle. UAS-ArcAβ42 and elavGS transgenic flies were backcrossed into w1118, as reported in 2 and wDah; dilp2-31,5 deletion mutants and Wolbachia-positive white Dahomey (wDah) controls are those reported in 3 . All genetic constructs were back-crossed into the genetic background of their control for at least six generations before experiments were performed.
For all experiments using adult flies, other than food choice, flies were reared on sugar, yeast food (1SYBrewer’s; 1SY) as described in 4 for lifespan experiments. Egg collections were used to synchronize fly age as described in 5 . Flies for the food choice assay were reared in a medium containing, per liter, 80 g cane molasses, 22 g beetroot syrup, 8 g agar, 80 g corn flour, 10 g soya flour, 18 g yeast extract, 8 ml propionic acid, 12 ml nipagin (15% in ethanol).
For all experiments using adult flies, other than food choice, flies were reared on sugar, yeast food (1SYBrewer’s; 1SY) as described in 4 for lifespan experiments. Egg collections were used to synchronize fly age as described in 5 . Flies for the food choice assay were reared in a medium containing, per liter, 80 g cane molasses, 22 g beetroot syrup, 8 g agar, 80 g corn flour, 10 g soya flour, 18 g yeast extract, 8 ml propionic acid, 12 ml nipagin (15% in ethanol).