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BiologyThe comma is bivoltine, which means that two generations are produced each year (3). It has a complicated life-cycle, with adults of the first brood flying in July, and those of the second flying in late August and September (4). Eggs are laid singly on leaves of the foodplants (nettles, elm, hop, currants and willows). They hatch after two or three weeks and initially the caterpillars spin webs on the undersides of the leaves. Once their bird-dropping camouflage has developed, they emerge into the open (4). The caterpillars suspend their pupae from stems and 2-3 weeks later the adults emerge. Some of these adults mate immediately, giving rise to the second brood of adults in late August or September. However, other adults of the first brood are not sexually mature after emerging from pupation; they spend their first summer feeding and then hibernate, mating the following year. As a result, the adults that emerge after hibernation consist of a mix of first and second brood adults (4).