Australian fritillary butterfly
Common name: Australian fritillary
Scientific name: Argyreus hyperbius inconstans
Family: Nymphalidae
Conservation status: The Australian fritillary butterfly is Endangered in Queensland (Nature Conservation Act 1992) and it is ranked as a low priority under the Department of Environment and Resource Management Back on Track species prioritisation framework.
Description
The adult male Australian fritillary butterfly is light orange above, with rounded black spots and a double black subterminal line - a line near but not precisely along the edges of its wings. Beneath the forewing it is pinkish orange, with the apex light orange, and otherwise marked as above. The hindwing is light orange with black markings edged with silver. The female is similar above to male, but its ground colour is paler orange with apical, subterminal and terminal black markings rather more pronounced than in the male, sometimes with the apex of the forewing and hindwing tinged with green.
Habitat and distribution
Most specimens have been collected from river estuaries or swampy coastal areas at or near sea level. The Australian fritillary butterfly is restricted to open, swampy, coastal areas where the larval food plant, Viola betonicifolia, grows as a small, insignificant ground herb in association with Lomandra longifolia (long leaved matrush) and grasses, especially the grass Imperata cylindrica (bladey grass). This habitat is called Melaleuca wetlands, although the larval food plant does not occur in all sub-types of this plant community. It is also sometimes found in disturbed areas (e.g. the drainage ditches of sugarcane farms) or in association with water course plant communities when its food plant Viola betonicifolia is present.
The Australian fritillary butterfly has been recorded in south-eastern Queensland and north-eastern New South Wales between Gympie and Port Macquarie. Of the 23 recorded localities only four have extant (still existing) populations. The historic sites at Glenugie Creek near Grafton (1895), Ballina (1898), Billinudgel (1910), Lauderdale (1911) and Indooroopilly (1916) among others, were some of the first to be lost in the almost catastrophic trend which has followed, resulting in a range contraction of greater than 80 percent.
Life history and behaviour
Adults fly in moist or swampy places where the larval food plant grows, feeding at flowers and settling on low vegetation or on the ground. Adults can be expected throughout the year although there is presently no evidence of the adult presence in September.
One report states that in midsummer the eggs hatch in about five days and the pupal duration is seven to nine days. However, other observations about the life history recorded a larval duration of four instars over 23 days, and a brief pupal duration of only four days. It was found that all adults emerged in the morning and females, when about to oviposit (lay eggs), settle on the ground and crawl about in search of the host plant, which is intertwined among other ground plants. Females lay on the host plant or leaves of plants over which the host is growing.
The Australian fritillary butterfly is characterised by 'boom and bust' cycles of adult abundance. Adults usually occur at low densities, but on occasions they are locally very abundant. The biological basis for this 'boom and bust' cycle is not well understood. It is thought that moderate densities of the food plant, Viola betonicifolia, in coastal wetlands are necessary to sustain breeding. As the plant density varies with drought, this mgiht impact on the butterfly's breeding.
Threatening processes
Habitat destruction is a known threat to the Australian fritillary butterfly. Habitat destruction has occurred due to coastal development, burning, drainage of wetlands and farming (which includes the use of herbicides). Investigation at a site near Condong found that the area had recently been sprayed with herbicide and the drains around the cane fields had been cleared and the host plants Viola betonicifolia destroyed'.
Other possible threats include the invasion and predation by introduced ants (e.g. fire ants (Solenopsis invicta) and coastal brown ant (Pheidole megacephala), weed invasion that impacts on the food plant Viola betonicifolia and uncontrolled butterfly collection at sites essential to the Australian fritillary.
Recovery actions
The Action Plan for Australian Butterflies suggests:
- Permanently protect the remaining localities with extant populations from disturbance (including clearing or drainage).
- Undertake weed and fire management for existing habitats.
- Undertake and encourage community participation in rehabilitation (if necessary by growing and planting Viola betonicifolia from local sources) at sites where the Australian fritillary butterfly has been found to occur, and where food plant numbers have declined.
- Undertake surveys to identify additional locations of breeding populations of Australian fritillary butterfly.
- Carry out studies on the development of immature and adult stages of the butterfly to understand the boom and bust cycle of this species.
Last updated 7 December 2011