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BiologyThe main foodplants of the caterpillars are cuckooflower (Cardamine pratensis), and garlic mustard (Alliaria petiolata); although a range of other members of the crucifer family are used (2). A single generation is produced each year (3); adults usually fly between mid-April and mid-June (2), and females lay eggs singly during May or June on the flower heads of the foodplants (3). The eggs, which are white at first, turn orange after 2-3 days, and are easy to spot (2). It is very rare to find more than one egg on a flower; studies have shown that females mark the flowers on which they have laid an egg with a pheromone, and other females are deterred from laying there as a result. This ensures that each larva has sufficient food in its early stages (2). During June and July (3) the caterpillars feed on the developing seeds in the flowers (2), they are also reported to be cannibalistic; if more than one egg is laid on a plant, this cannibalism gives one caterpillar an advantage, as it eliminates the competition (2). Caterpillars pupate in July (3) on tall vegetation near the foodplant (2), where they spend the winter as a pupa. The adults typically emerge the following May (3), although it has been discovered that in captivity, emergence can be delayed for up to two years, which may prevent an adult facing unsuitable conditions (2).