Butterflies are important members of your garden ecosystem, and they can tell us a great deal about our changing climate.
Most of us love to see pretty little butterflies fluttering gracefully around their garden, but caterpillars are a lot less charismatic. They are basically sausages with legs that eat your garden, but most plants can withstand a lot more caterpillar feeding than we give them credit for. After all, if your garden isn’t being eaten, it isn’t an ecosystem!
Also, not all caterpillars eat leaves. Some live within ant colonies and trick the ants into feeding them, or they just eat ant larvae because they live in a smorgasbord! They get away with this because they mimic the colony smell that ants use to recognise their colony mates, or even the sounds that a queen makes when she wants her servants to feed her. Tricky little caterpillars.
Their trickery extends beyond feeding. Most butterflies wear variations of browns and yellows, and they are being quite honest, but some get all fancy in iridescent blues, greens and purples. These butterflies are not to be trusted!
You see, butterflies only have one pigment, melanin, which is basically brown, so in order to produce bright colours they need to trick you into seeing something that isn’t really there. They do this using structural colouration.
Structural colouration is where microscopic structures interfere with light in the same way that a soap bubble does, to produce the illusion of colour. In butterflies, it is caused by the tiny scales which cover the wings being very thin and somewhat transparent, so that light refracts as it passes through them. This creates the optical illusion of brilliant blues, greens and purples when the wing is actually a drab brown. Lots of birds use this trick too, from peacocks to backyard roosters.
This isn’t the only way that butterflies are a bit odd; they have taste receptors on their feet so they know when they land on nectar-laden flowers, and they have light sensors on their genitals so they can position themselves just so on the chosen flower, and their eyes can see ultraviolet light so they see the world very differently to us. They are beautiful little weirdos, and important pollinators which we can encourage in our gardens.
The problems start when gardeners and farmers start spraying to get rid of caterpillars, because obviously this also gets rid of butterflies. One of our most hated agricultural pests, cutworms, pupate to become our beloved Bogong Moth, which is an important food for the Mountain Pygmy Possum. In ecology, everything is connected.
Butterflies are a canary in the coal mine for climate change. Their short generation time and reliance on environmental cues for various life stages makes them particularly sensitive to changes in the environment. For example, research has found that the Common Brown butterfly is emerging ten days earlier than it did 65 years ago due to increasing temperatures. Many butterflies (and other flora and fauna) worldwide are changing their ranges to follow the climate they prefer, moving north or increasing elevation. All this adaptation is great, but it has the potential to disrupt ecological associations between caterpillars and their food plants, or butterflies and the plants they pollinate.
To support butterflies and moths in your garden, you have to think about their whole life cycle. Plants that encourage egg-laying and provide food for caterpillars include ground covers such as purple coral pea and running postman, grasses including lomandras and poas, and trees like wattles and bush peas. One of the biggest dangers for caterpillars is the spraying of pesticides, even natural products like pyrethrum and some strains of BT toxin can kill them.
To attract butterflies, it is all about flowers, the brighter coloured and sweeter smelling the better. They particularly like red, blue and yellow, and they prefer flat-topped flowers or inflorescences that they can easily land on. Daises, saltbush, and pea flowers are particularly good. Moths prefer white or dull flowers, particularly ones that open in the late afternoon or evening. Moths and butterflies both prefer nectar rich flowers. Many of our endangered moths and butterflies prefer specific plants, so look up what species might live in your area for more specific planting ideas.
Around Canberra, growing wallaby grass for the golden sun moth is a great idea, but don’t despair if you don’t see them, they are very secretive! Having a protected sunny spot for butterflies to bask in is a great idea, as is a safe place for them to drink.