Europe’s large white butterfly became New Zealand’s unwanted guest
Pieris brassicae, the large white or cabbage butterfly, is a Pieridae relative of the small white. Common from Europe through North Africa to the Himalayas in farms and parks, it later rooted in South Africa and turned up in Nelson, New Zealand, in 2010 as a crop pest.
The large white goes by many names: cabbage butterfly, cabbage white, large cabbage white in India, and, wrongly, cabbage moth. It belongs to the family Pieridae and is a close cousin of the small white, Pieris rapae. It thrives across Europe, North Africa and Asia as far as the Himalayas, favouring farmland, meadows and parks, and has established itself in South Africa. A strong flier, it crosses to Britain from the continent in most years, topping up the local population. Scattered reports from Maine, Rhode Island and New York across the last hundred years are treated as doubtful, most likely stowaways or deliberate releases, but they raise the risk of the pest settling in North America.
In 1995 scientists predicted it would reach Australia and New Zealand, and in 2010 it turned up in Nelson, where it was dubbed the great white butterfly and listed as an unwanted pest because of the threat to crops. In October 2013 the Department of Conservation briefly paid a bounty: in two weeks the public handed in 134 butterflies at $10 each. Backed by over 263,000 property searches in the northern South Island and the introduction of predatory wasps, the campaign worked, and New Zealand declared the species eradicated in December 2014.
Eggs start pale yellow, deepen in colour within a day, and turn black a few hours before hatching, when the shell grows see-through and the larva shows inside. Caterpillars moult four times, passing through five stages. First-stage larvae are soft, pale yellow and hairy with brown heads; by the third stage they are yellow speckled with black and eat ravenously, doing most of the damage to host plants, and by the fifth they are long, sturdy cylinders.
Adults have white wings with black forewing tips, and females add two black spots on each forewing. The pale greenish undersides camouflage a resting butterfly, and summer broods carry darker markings. Wingspans average 5 to 6.5 cm.
Source: Pieris brassicae
