The air is dotted with hundreds of tiny bright white and black forms drifting purposefully across the landscape. In the city, one might be forgiven for thinking that someone is carelessly tossing shredded paper into the wind. But for once, litterbugs are not to blame for what’s blowing around Nairobi. These are not pieces of paper drifting aimlessly about, but hundreds of living butterflies on the move.
Clouds of white butterflies are currently making their way cross-country all over East Africa, drifting and swirling by in their hundreds. The butterflies can be seen on most sunny days around Nairobi, on the grasslands and riverine areas of the Nairobi National Park and at open green spaces within the city, such as the Arboretum and City Park.
These butterflies are broadly known as the Caper Whites. They are in the genus Belenois, and are a common feature of open woodland and grassland areas across the region. They fly restlessly, pausing often to sip nectar from flowers of every kind. They also gather at damp spots – even by roadsides with busy traffic. The males gather to mud-puddle at damp spots where they can form large congregations depending on the kinds of salts available and prevailing weather. One of the commonest species is the Brown-Veined White, Belenois aurota, where the veins on the underside of the white wings are outlined in brown-black.
The Caper White caterpillars feed on Maerua, Capparis and other members of the Capparaceae. The exact reasons behind these mini-migrations that occur periodically depending on the seasons are not fully understood. They could just be driven by instinct to disperse, but it is more likely that there are peaks in population growth that depletes caterpillar food-plants and forces the butterflies to move in search of new areas to lay eggs.
Keep an eye out for these incredible butterflies on their chaotic journey cross-country. Let us know if you have seen them!
By Dino Martins