The white pilgrims

Correcting some common misconceptions about the Great Little White Butterfly Migration.

By Justin Bode

A common sight towards the end of December and early January in years after good rains is large swarms of white butterflies flying across the country. These swarms are largely made up Belenois aurota, the Brown-veined white or Witgatwitjie butterflies.

These Great Little White Butterfly Migrations are every bit as spectacular as more famous ones, such as the annual wildebeest migration of the Maasai Mara in Kenya. Something about these epic movements of living creatures affects us deeply, and the feeling is strengthened when the creatures are as fragile as butterflies. These butterfly migrations have given rise to a number of myths or urban legends, among them that the butterflies are making for Madagascar.

In southern Africa, core populations of the Brown-veined Whites originate from the Karoo and Kalahari. These populations owe their strength to the main food plant of the caterpillars, the Shepherd’s Tree (Boscia albitrunca; Witgat (Afrikaans), Mohlôpi(Sotho),  Motlôpi (Tswana), Muvhombwe (Venda), Umgqomogqomo (Xhosa), Umvithi (Zulu)). These core populations are maintained by the females laying eggs on the trees before they set off on their migration.

The Great Little White Butterfly Migration appears to fall within the technical definition of a migration as they are “a seasonal journey to a different location… usually in response to changes in seasonal climate and food supply, often travelling very long distance along predetermined routes.”[1] This seasonal migration takes place from the south-western, more arid parts of Southern Africa to the moister north-eastern parts during mid- to late summer.

While it’s true that some of the butterflies do fly beyond the east coast, there is no evidence of any butterflies originating in South Africa actually reaching Madagascar, where the species is also found. Brown-veined Whites occur over a very wide area in Africa and into India. It’s also not clear whether populations outside of South Africa experience the same sort of swarming behaviour, though there is one recorded instance of an estimated 4-plus million Brown-veined Whites migrating between the Aberdares and Mount Kenya in the 1970s.[2]

It should be noted that not all Brown-Veined Butterflies migrate, nor do migrations necessarily take place every year.

Other myths/ urban legends about these butterflies are that they are responsible for crop damage, that they spread diseases and that they feed mostly on grasses. In fact, they feed only on the members of the Caper (Capparaceae) family and thus do not affect crops in any way. The Shepherd’s Tree is the main food species in the arid south-west, while other members of the Caper family are used in the eastern areas.

Moreover, there is no scientific correlation between butterfly migrations and the spread of pests or diseases—it’s surmised that any apparent correlations are coincidental, relating to the fact that current conditions happen to favour both.

The Great Little White Butterfly Migration is the subject of a citizens’ initiative to gather data to allow for a better understanding of this event. It is a joint project of the Animal Demography Unit of the University of Cape Town and the Lepidopterists’ Society, and part of the wider LepiMap project, which encourages members of the public all across Africa to submit photographic observations of butterflies and moths in order to understand their distribution and conservation status.

So if you observe any part of the Great Little White Butterfly Migration, why not log your observations on the Facebook page and become a citizen scientist.

More information

In view of widespread interest in the current Great Little White Butterfly Migration (Jan/ Feb 2020), LepSoc has put out a release, and expert Renier Terblanche has put a summary of recent research.

[1] E Lawrence, Henderson’s Dictionary of Biology (15 ed), quoted in Renier Terblanche, “Butterfly migrations gracing the face of Southern Africa in summer”, Babbel Blues 1 (Autumn 2014), p 16.

[2] TB Larsen, “A migration of Anaphaeis aurota F. in Kenya”, Deutsche Entomologische Zeitschrift, quoted in Terblanche, op cit Note 1.

Sources

S Mecenero, JB Ball, DA Edge, Ml Hamer, GA Henning, M Krüger, EL Pringle, RF Terblanche, and MC Williams (eds), Conservation assessment of butterflies of South Africa, Lesotho and Swaziland: Red List and atlas. Saftronics (Pty) Ltd: Johannesburg & Animal Demography Unit, Cape Town, 2013.

MC Williams, Afrotropical Butterflies, www.metamorphosis.org.za, 2016.

S Woodhall, Field Guide to Butterflies of South Africa. Struik, Cape Town, 2005.

Renier Terblanche, “Butterfly migrations gracing the face of Southern Africa in summer”, Babbel Blues 1 (Autumn 2014).