EXPLAINER: What's with the white butterflies flying across SA?

These white butterflies have been spotted in provinces such as KwaZulu-Natal, Gauteng, Free State and Northern Cape, leaving many wondering what they are and where they come from.

The brown-veined white butterfly. Picture: Sethembiso Zulu/EWN.

JOHANNESBURG - Over the past few weeks, South Africans have been treated to the wonderful sight of white butterflies flying across the sky.

These butterflies have been spotted in provinces such as KwaZulu-Natal, Gauteng, Free State and Northern Cape, leaving many wondering what they are and where they come from.

Eyewitness News spoke to Dr Vaughn Swart from the Zoology and Entomology department under the University of the Free State's faculty of Natural and Agricultural Sciences to understand more about these butterflies.

Dr Swart explained that the official scientific name of the butterfly species is Pieridae and in simple terms, the butterfly is known as the brown-veined white butterfly. What's happening is called the annual white butterfly migration, which happens around mid-summer time in South Africa.

"The butterflies originate from arid places in the country such as the Karoo and head in a north-easterly direction towards Mozambique and northern KwaZulu-Natal."

Dr Swart said the butterflies are an important part of the ecosystem as they serve as food for other insects and birds.

The number of butterflies migrating every year depends on the food available to them from the areas they originate, which in term affects how they pupate and lay eggs. Numbers differ from year to year.

"It can take between two to four days for the brown-veined white butterfly to reach its destination as it flies across the country," Dr Swart explained.