Bulloak jewel butterfly
Common name: Bulloak jewel butterfly, jewel butterfly
Scientific name: Hypochrysops piceata
Conservation status: The bulloak jewel is Endangered in Queensland (Nature Conservation Act 1992) and is ranked as a high priority under the department's Back on Track species prioritisation framework.
The bulloak jewel is small butterfly (wingspan 23-25 mm). Females are larger than males with broader and more rounded wings. The adult male's wings are dull purple above, while the females are pale blue. On the underside of the wings, both sexes are a brownish grey with spots and bands of orange or orange-red. The edges of both sides of the wings are black and metallic green. The hindwing has a very prominent rounded black spot edged in orange-red and the veins are shaded with brown-black.
Habitat and distribution
The habitat requirements of the bulloak jewel are complex. It requires a single species of tree, bull oak Allocasuarina luehmannii, an undescribed ant, Anonychomyrma sp., and possibly also the presence of eriococcid scale insects Rhyzococcus sp. Only older trees appear to be used by the bulloak jewel as these are riddled with the xyloryctid moth tunnels which encourage nesting colonies of the ant and provide shelter sites for the nocturnal butterfly larvae.
The bulloak jewel has a very restricted distribution and is only known from several small patches of habitat west of the Darling Downs near Leyburn and Goondiwindi. It originally occurred at Mt Emlyn near Millmerran, but has not been seen there since 1967. Since 2000, the bulloak jewel has been confirmed (through specimen collection) at two sites; Ellengowan Nature Refuge and Bendidee National Park. Additional sightings have been reported south-west of Cecil Plains but are yet to be confirmed.
Life history and behaviour
The bulloak jewel appears to have a mutual relationship with the ants. The species has been recorded to aggregate about bull oak trees occupied by the attendant ant during spring and late summer-autumn. The ant is thought to provide necessary protection for the butterfly larvae from parasites and predators, including wasps and spiders. In return the ant earns nutritious secretions (containing sugars and perhaps more importantly, amino acids) produced by glands on the caterpillars back.
The bulloak jewel likely lays its eggs on branches of the bull oak trees only when the particular ant is present. The ants attend eriococcid scale insects and the intense ant activity associated with the scale may attract pregnant female butterflies, which settle and then crawl on the host plant (Dunn and Kitching 1994; Greenslade 1995). The larvae shelter during the day in holes formed by xyloryctid moth larvae normally in the upper branches of the bull oak trees.
Males perch at heights of 9-15 m on the bull oak trees or sometimes on foliage of adjacent trees. Females may be found lower in the canopy (approximately 5 m) where ant density is high. They perch with wings closed or partially opened in a characteristic V-shape and remain perched for extended periods. Perching behaviour commences at approximately 11am with most activity in the afternoon, diminishing around dusk. However, females may be more active in the morning.
Adults feed on the nectar of flowers, the spring brood often forage at either the yellow flowers of Jacksonia scoparia, which are the dominant flowering plants at that time of year, or species of Eucapyptus. Jacksonia scoparia is not in flower during summer and it is likely that the summer adults rely on mistletoe flowers and flowers of Angophora trees. The species is also known to forage at flowers of Amyema linophyllum, Amyema miquelii and Amyema quandang (Dunn and Kitching 1994). The larvae are nocturnal feeders and are known to feed on the recent, upper growth of the bull oak trees.
The species restricted distribution and special habitat requirements make it particularly vulnerable to threats. The main threats known to affect the bulloak jewel include:
- The destruction of its habitat. Much of the habitat has been destroyed near the type locality at Leyburn by road widening and tree felling back in the early nineties. Old bull oak trees survive mostly among roadside native bushland remnants but they are vulnerable to being cleared for road widening.
- Removal of bull oak trees or fallen logs for firewood and commercial wood turning can destroy ant nests and restrict ant movement between trees.
- Burning of the undergrowth destroys the leaf litter necessary for the ants that attend the caterpillars.
There are a number of management actions that can help to secure the survival of the bulloak jewel, these include:
- Undertake further ecological research on the life cycle, population dynamics, dispersal ability, habitat requirements and plant / ant associations of the bulloak jewel to better effect management approaches.
- Continue to conduct surveys to locate and confirm any additional populations of bulloak jewel.
- Secure habitat protection for existing populations and work with the local community to help protect bull oak trees and surrounding native vegetation on privately owned land and roadsides.
What can you do to help this species
- Avoid burning undergrowth near and under stands of old bull oak trees.
- Keep a look out for the butterfly settling among bull oak tree canopies and report any potential sightings to your local Queensland Parks and Wildlife Office.
- Work with your local landcare or environment group to promote the protection of roadside and other remnants of vegetation containing bull oak trees.
- Don’t remove fallen logs from under bull oak trees as these provide nesting sites for ants that attend the caterpillars of the bulloak jelwel butterfly.
Braby, M.F. 2004. The complete field guide to butterflies of Australia. CSIRO Publishing, Collingwood.
Lundie-Jenkins, G. and Payne, A. 2000. Recovery plan for the bulloak jewel butterfly (Hypochrysops piceatus) 1999–2003. Queensland Parks and Wildlife Service, Brisbane.
Sands, D.P.A. and New, T.R. 2002. The Action Plan for Australian Butterflies. Environment Australia, Canberra.
Dunn, KL and Kitching RL 1994. Distribution, status and management of the piceatus jewel butterfly on the Darling Downs, Queensland. A report to the Queensland Department of Environment and Heritage, Conservation Strategy Branch.
Greenslade, P 1995. Leyburn’s bull oak roadside: the only current locality for Australia’s rarest butterfly, the Darling Downs jewel. Nomination for the register of the National Estate to the Australian Heritage Commission.