Butterflies in the suburbs

Native butterflies drift lazily through your backyard on sunny spring and summer days. Ever wondered where they come from? Did some all-powerful super-being create them spontaneously from thin air and drop them in your garden? Why have they come to 27 Smith Street, Elwood? What are they doing?Published 13/07/12 | by John Reid

Butterflies like nectar. Nectar from all kinds of flowers, indigenous and exotic. The carbohydrates contained in this nectar help them to live longer, give them the strength to find a mate and breed successfully, enabling the females to produce lots of viable eggs.

So it seems our adult butterflies are happy with many of the plants we serve them up in those crazy, chaotic, jumbled collections of flora we surround our houses with. But adult butterflies are essentially breeders, and as we have seen, they appear to be fairly unspecific in their choice of plants to provide strength-giving nectar. It is when the eggs hatch out to produce caterpillars (larvae), that the crucial feeding stage begins. And it is this stage that we must be most aware of if we are to conserve indigenous butterflies.

Like all indigenous fauna, butterflies require the correct habitat in which to live. In particular, this habitat must provide them with particular larval food plants. When the female butterfly is ready to lay eggs, her sense of smell is probably stimulated by the essential oils of the plant species on which the larvae can feed. Regardless of the nature of this stimulation, she usually lays her eggs on or near certain preferred plants. This ensures that when the eggs hatch, the young caterpillars will be on or close to the plant they want to start munching straight away.

That’s enough of the preliminary waffle: now for the guts of the article. We are all land managers in our own way, professional or otherwise. We can all have input into the way our indigenous flora and fauna are managed. For example, in suburban Melbourne we can get involved in our own gardens, in council reserves, bits of bush along the roadsides, railway lines, creeks and gullies, etc. As lovers of indigenous flora and fauna, let’s have some input on behalf of the caterpillars of our native butterflies.

Spiny-headed Mat-rush (Lomandra longifolia), a common local tussock of the grasstree family, is the food plant for at least two species that occur around Melbourne: the Splendid Ochre or Symmomus Skipper (Trapezites symmomus), and the Barred or Dispar Skipper (Dispar compacta). Wattle Mat-rush (L. filiformis) is eaten by the Montane Ochre or Phigalioides Skipper (T. phigalioides).

Native grasses are particularly valuable as butterfly habitat. There are at least seven other Melbourne butterflies that feed exclusively on grasses such as Kangaroo Grass (Themeda triandra), Blue Tussock Grass (Poa poiformis) and Slender Tussock Grass (P. tenera). These include the Common Brown (Heteronympha merope), Shouldered Brown (H. penelope), Ringed Xenica (Geitoneura acantha) and Klugs or Marbled Xenica (G. klugii).

The general public doesn’t seem to be particularly enamoured by our parasitic (shock! horror!) native mistletoes. But we must tell all those who don’t love these plants that as well as a host of other ecological values, they provide larval food for at least four Melbourne butterflies: the Imperial White or Imperial Jezebel

(Delias harpalyce), Wood White or Spotted Jezebel (Delias aganippe), Olane or Broad-margined Azure (Ogyris olane) and Dark Purple Azure (O. abrota).

The Imperial White is a particularly beautiful insect, black and white on the uppersides of its wings with splashes of red and yellow against a dark background on the undersides. Around Melbourne it usually has two generations each year. The adult butterflies fly around looking spectacular between September and November, then a second generation hatches in February and flies till April. Their caterpillars feed on the leaves of various mistletoes. In the suburbs of Melbourne these include Creeping Mistletoe (Muellerina eucalyptoides), Drooping Mistletoe (Amyema pendulum) and Box Mistletoe (A. miquelii).

Two of our local Saw-sedges (Gahnia sieberiana and G. radula) are excellent butterfly plants, providing food and shelter for the larvae of the Sword-grass Brown (Tisiphone abeona), Donnya or Varied Sedge-skipper (Hesperilla donnysa) and Spotted Sedge-skipper (H. ornata). If we can both preserve and re-establish these two sedges within the appropriate vegetation associations along verges and in bushland remnants, these three butterflies may continue to fly in the suburbs of Melbourne.

Another handsome butterfly of the Melbourne area is the Australian or Yellow Admiral (Vanessa itea), black and rich port wine coloured with a large cream patch on each forewing. Its caterpillars feed at night on the leaves of the native Scrub Nettle (Urtica incisa). During the day they hide in a shelter made by joining a couple of the nettle leaves with a few strands of silk.

Along Dandenong Creek in Heathmont, there still occurs* at least one colony of the Common Imperial Blue or Imperial Hairstreak (Jalmenus evagoras). They have survived in this area because two of their food plants, Black Wattle (Acacia mearnsii) and Silver Wattle (A. dealbata) have been retained near the creek. Here the larvae and pupae are attended by swarms of small black Iridomyrmex ants. The ants harvest sweet secretions from the larvae and pupae, and presumably return some degree of protection from predators. I have found colonies of the Common Imperial Blue in Mount Waverley, Vermont South, Donvale and Warrandyte.

The Common Grass-blue (Zizina labradus) is regarded as the most abundant butterfly in Australia. The caterpillars feed on the young leaves, flower buds and seed-pods of various pea flowered plants. Around Melbourne, they probably feed largely on introduced legumes such as White Clover (Trifolium repens) and Lotus species, but many indigenous species have been recorded as food, including species of Desmodium, Swainsona and Indigofera. The Two-spotted Line-blue (Nacaduba biocellata), is a smaller but prettier butterfly with larvae that feed on the flowers of a large number of Acacia species.

Another group of much maligned indigenous Melbourne plants are the Dodder Laurels (Cassytha spp.). They are often thought of as straggly and untidy, and of course like the mistletoes they are p-p-parasitic! As well as growing in dense tangles that provide safe places for native birds to nest, they are also the food plant of the larvae of the Common Duskyblue (Candalides hyacinthina). I have found these caterpillars on one of the Dodder Laurels, probably Cassytha melantha, in open forest dominated by Red Box, Long-leaf Box and Red Stringybark in Warrandyte and Park Orchards.

There are other indigenous butterflies and indigenous butterfly food-plants in the Melbourne area, but this lot will do for a start. It is hoped that this article will stimulate further discussion by IFFA, on how we can promote public awareness of all indigenous invertebrate animals and their habitat requirements.

This article was originally published in Indigenotes Newsletter No. 4 September 1986. IFFA intends to re-publish a series of articles which the late John Reid wrote for Indigenotes during 1986 and 1987, in recognition of his contribution to advancing our knowledge and protection of our indigenous flora and fauna. Thanks also to Graeme Lorimer and Ian Faithfull for updates and corrections to the article.

Michele Arundell, IFFA Secretary.