Large White (Pieris brassicae) in Ireland

Bánóg mhór in Gaeilge. The Large White, Pieris brassicae, is the biggest of the three common Irish whites and the one Irish allotment growers know as a brassica pest.

Identify it in four steps

1. Upperside forewing carries a strong, solid black wedge extending down the outer margin, deeper and more clearly bordered than in either Small White or Green-veined White.
2. Females carry two black spots on the forewing upperside; males carry none, distinguishing sexes at a glance.
3. Underside hindwing plain cream-yellow without the green-grey vein shading of the Green-veined White.
4. Wingspan 58 to 70 mm, clearly larger than Small White (40-52 mm); flight strong, direct, and often high across gardens.

Habitat in Ireland

The Large White is a garden, allotment, and farmland species that also uses coastal cliffs and rough ground where wild crucifers grow. Numbers in Ireland are augmented each summer by continental migrants, sometimes arriving in visible waves along the south and east coasts.

Larvae feed communally on cultivated brassicas (cabbage, kale, Brussels sprout, oilseed rape) and on wild crucifers including Nasturtium (Tropaeolum majus) in gardens. Larval clusters are yellow-and-black warning-coloured, sequestering mustard-oil defences from the foodplant.

Where to see it

• any south-coast garden, County Cork: migrant waves often make landfall on the south coast from May onward.
• Dublin allotment sites (St Anne’s, Bushy Park): brassica plots reliably produce breeding adults through summer.
• the Copeland Islands, County Down (Northern Ireland): migrants recorded regularly along the coastal edge.

Related species

• Small White (Pieris rapae)
• Green-veined White (Pieris napi)
• Brimstone (Gonepteryx rhamni)