Bull oak jewel butterfly
Common name: Bull oak jewel, jewel butterfly
Scientific name: Hypochrysops piceata
Legislative name: Hypochrysops piceatus
Conservation status: The bull oak butterfly is 'Endangered' in Queensland (Nature Conservation Act 1992).
Description: The adult male is dull purple above. Its forewing has a broad brown-black edge suffused with orange-yellow. The veins on the forewing are suffused with orange. The hindwing is also edged with a broad brown-black border. The hindwing veins are suffused with orange. The underside of the bull oak jewel's wings are brownish grey with spots and bands of orange or orange-red, edged both sides with black dusted metallic green, and have a sub-terminal band on both wings with a light metallic blue outer edge and a black inner edge. The hindwing has a very prominent rounded black spot surrounded by an orange-red tornal spot. The female is bluish purple above, with wings more rounded than in male and the costa and termen (edge of wing) are broadly brown-black. The veins on the hindwing are suffused with brown-black. The underside of the wings is the same as in the male.
Habitat and distribution: The habitat requirements of H. piceatus are complex. It requires a single species of tree, bull oak Allocasuarina luehmannii, and an undescribed ant, Anonychomyrma sp., and possibly also the presence of eriococcid scale insects, Rhyzococcus sp. to possibly facilitate ant aggregations and permit gravid female butterflies to home in on ant-occupied host trees. Only older trees appear to be utilised by the butterfly 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 bull oak tree host is widespread in eastern Australia, it requires sandy soils which are often of low fertility. The ant is also found on a small number of other bull oak sites nearby but, despite an intensive search in all similar habitat that can be found in the region at appropriate seasons and times of day, no other populations of the bull oak jewel have been found.
Recent surveys have determined that there are six sites within a 5 km radius, not far from Toowoomba, where bull oak jewel butterfly occur. Most recently the butterfly has been recorded at Bendidee National Park, which represents a major expansion of species range and provides hope that the species may be located in similar habitats to the north.
Behaviour and life history: Bull oak jewel aggregate about Allocasuarina luehmannii (bull oak tree) occupied by the attendant ant Anonychomyrma sp. during spring and late summer-autumn. Males perch at heights of 9-15m on the larval host or rarely on foliage of adjacent trees. Females may be found lower in the canopy (approximately 5m) where ant density is high. They will remain perched for extended periods, males will investigate approaching H. piceatus or Ogyris sp. adults. They perch with wings closed or partially opened in a characteristic V-shape. Perching behaviour commences at approximately 11am with most activity in the afternoon, diminishing around dusk. Females may be more active in the morning. H. piceatus has a slower, more fluttery mode of flight than the cyane jewel butterfly, H. cyane which occurs in the same habitat.
Eggs of the bull oak jewel are probably laid on branches of the bull oaks close to areas of intense ant activity. The ants attend eriococcid scale insects and the intense ant activity associated with the scale may attract gravid female butterflies, which settle and then crawl on the host plant. The larvae shelter during the day in holes formed by xyloryctid moth larvae normally in the upper branches of the bull oaks and are attended by the ant. Larvae emerge to feed at night and probably pupate in these same shelter sites with the ants.
Threatening processes: The main threat known to affect the bull oak jewel is habitat destruction while suspected threats are the collection of individuals and removal of bull oak trees. Because the remaining area of habitat is so small, events such as roadside fires pose a real threat to the existence of H. piceatus.
Recovery actions:
- An autecological study (a study of the bull oak jewel alone) is essential to gain a complete understanding of this species' requirements, and the reasons for its limited distribution.
- Agreement to maintain vegetation from the roadside and adjoining privately owned land on which suitable vegetation exists near Leyburn to stop ongoing and complete habitat loss.
Further information:
Sands, D.P.A. and New, T.R. 2002. The Action Plan for Australian Butterflies, Environment Australia, Canberra.
Recovery plan for the bull oak jewel butterfly (Hypochrysops piceatus) 1999-2003
Last updated: 31 August 2006