The lasting effects of multiple blood-feeding on the expression of insecticide resistance in Anopheles arabiensis SENN-DDT females. Mean percentage mortalities of 18 day old SENN-DDT females that either had no blood, a single blood meal (1 blood) or their fifth blood meal (multiblood) 4 hours prior to exposure were compared to that of 18 day old females that acquired their last blood meal at the age of 15 days (15 day blood; 18 day exposed). Insecticide bioassays were conducted 4 hours post blood meal except for the last cohort which was assayed against listed insecticides 3 days post blood-feeding (15 day blood; 18 day exposed). Only the mean mortality induced by the delayed deltamethrin treatment differs significantly from the mean mortality of the multiple blood meal cohort (multiblood) of the same age (p < 0.05). The effect of multiple blood-feeding on the expression of resistance was maintained for the DDT and permethrin resistant phenotypes 3 days post blood-feeding. Perm = permethrin; Delta = deltamethrin. The asterisks denote significant differences between 18 day multiple blood meal treatments and those exposed at 18 days but last fed 3 days prior to exposure. Lower case letters indicate no significant differences.