Overwintering adults emerge in spring and begin feeding and mating on flowering rush leaves, both above and below the water surface. Females chew holes in flowering rush leaves, lay 1–2 eggs per hole, and plug the holes with feces. Hatching larvae mine down towards the leaf base, often exit the leaf after a few days, and swim to another flowering rush leaf where they continue to mine down to the top of the rhizome. Pupation occurs in a pupal chamber in the lower part of leaves and flowering stems. Adults remain inactive in their pupal chamber for several days before emerging. Most emerging adults enter a period of aestivation where they remain inactive for the remainder of the summer before overwintering below water on or in plant debris or soil adjacent to the plant. Adults emerge again in spring and can survive at least two years. Thus, in any given year there are overlapping generations and ages of adult beetles; however, it is suspected only one new generation is produced each year. Bagous nodulosusadults have wings but have not been observed to fly during multiple years of rearing in Europe. It is suspected their primary mode of long distance dispersal is via passive spread on water currents.