Pieris brassicae

Lore & Background

The large white is a strong flier, and its British population is reinforced most years by migrations from the continent. Scattered reports from the northeastern United States over the past century are of dubious nature, indicating either accidental transport or intentional release. Such introductions threaten to establish this agricultural pest in North America. In 2010 the butterfly was found in Nelson, New Zealand, where it is known as the great white butterfly and classed as an unwanted pest. For a limited period in October 2013, the Department of Conservation offered a monetary reward for capture; the public captured 134 butterflies, netting $10 each. Combined with over 263,000 searches and release of predatory wasps, the large white was officially declared eradicated from New Zealand as of December 2014.

Reader's Guide

The large white butterfly is significant both as a common Eurasian species and as a notable invasive pest. Its larvae feed voraciously on cruciferous crops such as cabbages, Brussels sprouts, and oil-seed rape, causing substantial agricultural damage. The species demonstrates strong migratory behavior, with northern populations augmented by summer migrants from southern areas. Its life cycle includes two to three generations per year, with eggs laid in clusters on the undersides of leaves. The butterfly's ability to establish populations outside its native range—such as in South Africa and temporarily in New Zealand—highlights the risks of accidental or intentional introductions. The successful eradication campaign in New Zealand, involving public participation, extensive searches, and biological control, serves as a model for managing invasive insect species. The large white's close relationship with its host plants, which contain mustard oil glucosides essential for larval survival, underscores the ecological specialization that can make such species both vulnerable and destructive.

Did You Know?

• The large white is also called the cabbage butterfly, cabbage white, or cabbage moth (erroneously).
• In October 2013, the New Zealand Department of Conservation offered a $10 reward per butterfly, leading to the capture of 134 butterflies in two weeks.
• Female large whites use their forelegs to drum on leaf surfaces to test plant suitability before laying eggs.

Distribution and Invasive Potential

The large white butterfly is native to a vast stretch of the Old World, spanning Europe, North Africa, and Asia up to the Himalayan range. It is at home in agricultural areas, open meadows, and parkland. Because it is a powerful flier, the British population receives fresh arrivals from the continent in most years. Yet the species also demonstrates a capacity for invasive establishment. It took hold in South Africa, and in 1995 experts predicted a spread to Australia and New Zealand. That forecast came true in 2010, when the butterfly appeared in Nelson, New Zealand, where locals dubbed it the great white butterfly. Classified as an unwanted pest because of its threat to crops, it prompted a major containment campaign. In October 2013, the Department of Conservation offered ten dollars per captured specimen; within two weeks the public had netted 134 butterflies. Coupled with more than 263,000 searches across the upper South Island and the introduction of predatory wasps, these measures led to the species being officially declared eradicated from New Zealand in December 2014. Dubious historical sightings in New York, Rhode Island, and Maine over the past century continue to raise alarm about the possibility of accidental or deliberate introductions into North America.

Larval Development and Crop Damage

The large white caterpillar passes through four moults and five distinct instars before pupating. The freshly hatched first instar is a soft-bodied, light yellow larva with a conspicuous brown head and a notably hairy appearance. After the first moult, the second instar develops tubercles bearing black hair. The third instar marks a dramatic shift in behavior: the larva becomes more active, shifts to a brighter yellow coloration studded with black dots, and begins feeding voraciously, inflicting significant damage on its host plant. The fourth instar resembles the third but is larger in both size and appetite. By the fifth instar, the caterpillar is cylindrical, robust, and elongated, with vivid coloration on the thorax and abdomen and a grey-and-black head. This final stage demands the maximum in food quality and quantity to complete development; failure to meet that threshold results in the larva dying before it can emerge as an adult. Because the larvae feed on cabbages, Brussels sprouts, oil-seed rape, and other crucifers, the species is regarded as a serious agricultural pest wherever it establishes a population.

Wing Morphology and Sexual Dimorphism

Both sexes of Pieris brassicae display white wings with black tips on the forewings, and the average wingspan ranges from five to 6.5 centimeters. The underside of each wing is a pale greenish tone that provides excellent camouflage when the butterfly is at rest. Black markings tend to be darker in the summer brood. Males present a creamy white upperside; the forewing is sprinkled with black scales at the base and along the costa, while the apex and the area above vein 2 are broadly black with a regular inner curve. The hindwing carries a large subcostal spot before the apex. Females differ in several respects: the black irroration at the wing bases is more extensive, the black area on the forewing apex is broader with a less evenly curved inner margin, and a conspicuous large black spot appears in the outer half of interspace 1. The female's hindwing subcostal spot is notably larger and more prominent. On the underside, the female's forewing apex and entire hindwing surface are light ochraceous yellow rather than the male's ochraceous brown, and her discal black spots are substantially larger. Both sexes share black-and-white antennae and a black head, thorax, and abdomen with white hairs.

Reproduction and Life Cycle

Pieris brassicae typically produces two generations per year, with the first brood of adults emerging around April and the second around July. In sufficiently warm summers, a third brood may appear later in the season. Mating in this species is predominantly monogamous, though polyandry—where a single female mates with more than one male—does occur and is not the dominant pattern. Females lay their eggs in clusters. The ova begin as a pale yellow and darken to a deeper yellow within twenty-four hours of being deposited. As hatching approaches, a few hours before the larva emerges, the egg turns black and the shell becomes more transparent, revealing the developing caterpillar inside. The species' habitat preference for large open spaces, farms, and vegetable gardens—where wild and cultivated crucifers, cabbages, Brussels sprouts, and oil-seed rape are abundant—ensures that both feeding and reproductive sites are readily available. Butterflies are often observed hovering around walls, fences, tree trunks, and their food plants in these settings.