Sophia has been observing miraculous metamorphosis in her garden. This Earth Kid keenly recorded the Life Cycle of the Cabbage White Butterfly. Sophia’s butterfly took 37 days to complete the entire life cycle, from egg laying to metamorphosis!
Sophia’s Butterfly Story
The Cabbage White flitted about the vegetable garden, looking for a spot to lay her eggs. She laid her batch of tiny yellow eggs on the underside of a huge cabbage leaf and soon the tiny caterpillars hatched. These yellow creatures grew fast and by day 4 they had eaten so much that they had changed shape and colour.
On day 6, they moved to another cabbage leaf to eat and eat and eat. By day 14, the caterpillars had grown even more:” Whoa! Look at all the damage they have done!” exclaimed Sophia. “They have invaded the whole plant!”
She showed us the skins she found, left behind after the caterpillars had moulted. And she showed us how the worms got attacked by a parasitic wasp which laid its eggs on the caterpillars. On Day 20, the caterpillar started to spin their cocoons and a day later had reached full pupa stage. Day 37 was the Big Day of Freedom – the brand new butterfly emerged – a miraculous metamorphosis!
Cabbage White Life Cycle
We then did some background research and found out some really juicy titbits about this fascinating alien invasive insect. Sophia’s research was spot on! Here we add some more detail.
Cabbage whites are found in fields, gardens, parks and roadsides all over the world. Their life cycle is fascinating – miraculous metamorphosis – and goes like this:
- Mating: these butterflies mate tail to tail when they are about 2 to 3 days old.
- Eggs: female Cabbage White butterflies choose a host plant and place their rectangular white or cream-colored eggs one-by-one on the underside of a leaf.
- Host plants: include cabbage, cauliflower, broccoli, radishes, horseradish and nasturtiums.
- Incubation: it takes about 4 to 8 days for the eggs to hatch but this time length depends on the temperature.
- Larval Stage: Cabbage White larvae, called cabbage worms, are green with five lengthwise yellow stripes, and are covered with short fine hairs. The larvae spend their first week of life eating the underside of their host plant’s leaves. During their second week, they feed on the top of the leaves.
- Larval moulting: the cabbage worm grows so fast, he outgrows his exoskeleton and needs to moult during the larval stage. He chooses a dry spot on the host plant to moult. He spins a silk covering with a silk gland located below his jaws, attaching himself to the plant. His exoskeleton splits open, allowing the larva to crawl out.
- Metamorphosis: the cabbage white larva begins to pupate about 2.5 weeks after hatching. He attaches himself to the underside of a leaf or stem and spins a silk pad. The cabbage worm spins silk strands to attach himself to the silk pad. A brown chrysalis forms inside the exoskeleton. An outline of the wings appears during the first few days. Two dark wing spots will appear about 24 hours before emergence.
- Emergence: In warm weather, emergence occurs 30 to 45 days after the egg hatched. The cabbage white butterfly changed from a caterpillar to a butterfly during this time. His chrysalis splits open and the adult butterfly emerges. He pumps up his wings, then rests while they dry, before flying off to begin foraging.
- Adult Butterfly: adult Cabbage White butterflies pollinate plants as they feed on nectar from many flowers, including dandelions, red clover, asters, mint and strawberries.
The Story about the Cabbage White Butterfly
Pieris rapae is known in North America as the cabbage white or cabbage butterfly, and in Europe as the small white. It is a small- to medium-sized butterfly species of the whites-and-yellows family Pieridae. Here in South Africa we call it the Cabbage White and although we see it everywhere in spring, it is an exotic species.
We recognise the butterfly by its white color with small black dots on its wings. The caterpillar of this species, often referred to as the “imported cabbageworm“, is a pest to crucifer crops such as cabbage, kale, bok choy and broccoli.
The cabbage white or Koolwitjie, as it is known in Afrikaans, is South Africa’s only alien butterfly, and it is becoming a problematic invasive species. Andre Claassen first saw it in his garden in 1994 and has tried to track it down:
“It is not known exactly when the cabbage white arrived in South Africa, nor has it been established how it reached the shores of this country and nor do we know for certain where it came from. The butterfly may have reached the Western Cape as a migrant from Europe, where it is one of the most abundant species. Alternatively, eggs or caterpillars might have been introduced by accident on food plants such as cabbage. A third possibility is that somebody deliberately smuggled eggs or larvae into the country, reared them on cabbage, possibly in his own garden, from where they spread into surrounding areas.”
This butterfly species is doing well because survival conditions suit it so much:
- South Africa’s mild climate
- plentiful host plants on which to feed – nasturtium, sweet alysssum lobularia maritima, the annual weed rapistrum rigosum and, of course, cabbages – grown commercially and in private gardens.
Pieris rapae is widespread in Europe and Asia. Andre notes that it is native to Europe and was introduced to Canada in 1860. It spread across North America so fast that it reached California in 1883. It reached Hawaii within 10 years. In 1930 it reached New Zealand. Within a decade it had spread across Australia as well.
Controlling this Exotic Butterfly
Control measures include correct crop rotation, removal of plant debris from fields and deep seasonal ploughing. Cabbage White butterfly populations are kept under reasonable control, however, by the parasitic wasp Pteromalus puparum. Wasps kill the Cabbage White caterpillars and pupae which means that only a tiny percentage of the caterpillars reach their adult, reproductive stage.
Most people are unaware that the attractive and conspicuous butterfly in their garden is a foreigner and enjoy watching it. Andre says “Even my little four year old granddaughter proudly told me one day: ‘Grandpa I saw a white cabbage in our garden.”