Tanya Loos
Last summer we had an explosion of Cabbage White Butterflies which are an introduced species, and quite a few native Imperial Jezebels – and this year we are blessed with another black and white butterfly boom – this time the Caper White Butterfly!
Caper White Butterflies can be distinguished from Cabbage Whites and other species by the strong black venation pattern and margins on their wings, with yellow-orange spots on the underside of their wings. Cabbage whites have no orange colour.
Cabbage Whites, Imperial (and Painted) Jezebels and other local butterflies are seen in good numbers when their caterpillars do very well and many survive to adulthood. In the case of the Caper Whites, the large numbers we are seeing locally is due to the fact that they are on migration!
Caper Whites are so called because their larvae feed on the leaves of trees and shrubs in the Caper Family, Capparis, and also the Australian Sandalwood. But these species don’t grow locally. Capers such as Wild Orange (Capparis mitchelli) and Bush Caper (Capparis spinosa) occur in the drier, inland parts of Australia.
The species is strongly migratory – flying fast at about head height – sometimes for distances of over 3000 km. But even butterfly experts are mystified as to why adult Caper White butterflies would embark on these southerly migrations that take them away from their food plants.
Some sources suggest that their movements are related to weather and hot northerlies blow them out of their usual range towards the east coast. Our recent full on cold snap was, paradoxically, related to the intense heatwave conditions occurring inland. And then a couple of weeks later, thousands and thousands of these butterflies appear, so the notion that warm northerlies blew them in kind of fits. Migration is also very much part of their genetic make-up – this genus has closely related butterflies in Africa that also undertake mass migrations.
So, as the adults are passing through our region they are happily drinking nectar from all sorts of plants. I have seen them sipping on Rosemary, Daffodil and Onion Weed in my garden, and in the native forest here and near Castlemaine dozens of daisies and flowering native shrubs.
During a Caper White Butterfly migration event some adults find their way to the caper plants at the Royal Botanic Gardens Melbourne and successfully breed there!
Tanya Loos is a local naturalist, author and environmental consultant who loves to work in the environmental not-for-profit sector. She is the author of “Daylesford Nature Diary” available from her website or from Paradise Books in Vincent Street, Daylesford.
Have you got any nature questions for Tanya? Send them in!
