Butterfly Season

What a wonderful butterfly season we are having this year.
I suppose you have all noticed that this is a big year for caper whites (Belenois java teutonia)?
This is the butterfly with the fairly plain wingtops, white with black edging,


and the beautifully marked underside which you only notice if you look a little more carefully, or see one at rest.

I don’t think anyone knows quite why they sometimes have a spectacular year like this. We haven’t had one since before the 2011 floods, so perhaps they do better when the weather is dry.
People speak of them “migrating”, which suggests a purposeful journey with a planned end in mind. What they are really doing seems to be more of a random radiation. Perhaps they have exhausted their local host plants and are simply flying away in hope of finding more. They turn up in great numbers in the southern states where the host plants don’t occur naturally. There manage to find the few cultivated specimens, where they can be seen flying in a whirling mass around the plant. The males and females fly in separate migrations, but obviously succeed in meeting up, as they have been seen laying eggs in Victoria. (If they can’t find a caper plant, they lay on unsuitable plants, and the caterpillars die.)
They also fly out over the Pacific Ocean in their many thousands. Odd specimens have been known to turn up as far away as Samoa.
The butterflies breed on our local native caper plants, Capparis arborea, C. mitchellii, C. lasiantha and C. sarmentosa. Like most local butterfly host plants, gardeners rarely plant them, so the butterflies breed in the country and can only be enjoyed in our towns because they are strong flyers who will often drop in for a refreshing sip of nectar in our gardens. (Butterflies with less strong flying skills and migratory urges are disappearing from our urban areas, as they just can’t make the flight from the increasingly distant breeding sites.)
Most of our local native capers grow on country roadsides. They are prickly plants, so are grown only by butterfly enthusiasts, and tend to be cleared from farms and acreage estates by owners who don’t want to deal with the prickles.

They can also be completely defoliated whenever the butterflies have a big breeding year. They bounce back to beauty and good health afterwards, with all the freshness of a well-pruned plant, but the only people who grow them are those who value the cloud of lovely butterflies more highly than a high standard of year-round perfect beauty from their plants.
Roadsides are potentially subject to clearing for road-building, as our population increases, as well as “beautification” by those who prefer a well-mown, neat and tidy road verge to native vegetation. Depending on your personal aesthetic and philosophical viewpoint, a natural roadside environment is a rich and  environmentally productive ecology, or an ugly “hotch potch”. Unfortunately, destroying a patch of biodiversity is very, very much quicker and easier than replacing it, so the people who think nature needs tidying up, and are prepared to do something about it, have a disproportionate  advantage, when it comes to living in their preferred Australian landscape type.
The long-term future may hold fewer of these spectacular caper white population explosions. Let’s enjoy them while we have them.
For more on this butterfly and its host plants, see my posts for November 19, 2009 and December 4, 2008, or simply type the butterfly’s name into this site’s white search box at top left.