There always seem to be white butterflies about. Their whiteness stands out against the dull hues of the roadside bush. Almost all white and yellow butterflies in Australia belong to the one family, helpfully called the ‘whites and yellows’, or Pieridae to be technical. The very name ‘butter-fly’ comes from the colour of a UK species.
Conspicuousness is, of course, a warning – anything that says “look at me” like this is going to be pretty nasty to eat. Here in Helensburgh I’ve seen young innocent sparrows (if sparrows can ever be innocent) snapping up white butterflies and instantly spitting them out.
It seems that the poison is on the wings. Poisons vary slightly between species and one south-east Asian species in this group uses the same poison as the infamous cone snails.
The white that flops around your garden and along the road throughout most of the year is not native. It’s the ‘small white’ of the UK, here called the cabbage white (Pieris rapae), a major pest of brassica and mustards, which also tucks into nasturtiums.
The small white has only been with us since 1929 (Melbourne) and did not reach Sydney until 1943, but now it seems to be ubiquitous. The thin green caterpillar makes large irregular holes in leaves and eats developing buds. Our broccoli always gets clobbered by them. The adults are attracted to badminton, or at least lofted shuttlecocks – to chase off a giant intruder or to mate with a giant partner? Roadsides are highly disturbed habitats, plagued with weeds, so the whites you see there may actually be useful.
In the last month or so another, native, white butterfly has been around the Illawarra in huge numbers. This is the caper white (Belenois java), differing from the small white by black edging to the wings, with some yellow mixed in underneath.
I said native, but it’s not really a native around here, just a ‘migrant’, sporadically undergoing large movements south from its breeding grounds in western Queensland and north-western NSW. They die out here as the foodplants (native capers) are not available.
Why do caper whites commit mass suicide like this? No one really knows, but perhaps they are like lemmings or locusts, even humans, needing to move on after eating themselves out of home. And as our climate changes this mass movement strategy will help them (as a species) stay ahead of the game.
Have a great Christmas holiday break everyone and let’s hope 2021 is an improvement.
Have a question specifically for Dr Chris? Email editor@2515mag.com.au
