Explorer Ludwig Leichhardt called it 'exceedingly remarkable and bizarre'. University of Queensland researchers call it 'spectacular but threatened'.
Although avoided by predators, Leichhardt's grasshopper is threatened by annual burning in its Northern Territory savannah/sandstone habitat and by its own lack of mobility.
In 1845 Leichhardt observed this unique insect in great numbers in what is now Kakadu National Park. Leichhardt's grasshopper is now the subject of a University of Queensland study which may assist in saving it.
Australia's most spectacular grasshopper, Leichhardt's grasshopper Petasida ephippigera has an arresting brick-red, black and orange colour, with royal blue flashes.
Featured on an Australian stamp in 1991 and widely used in Northern Territory tourist brochures, the grasshopper now exists only as small isolated populations.
Such small populations of the grasshopper have been found in recent years within Kakadu National Park, at Keep River National Park (about 800km southwest of Kakadu) and in the Arnhem Land region.
Researchers Professor Bill Kitching and Dr Mary Fletcher, of the University's Chemistry Department, said little was previously known about this interesting insect, even among the local Aboriginal people of the Kakadu region.
Field work by collaborating CSIRO biologist Lyn Lowe has determined that the insect colonies are found only on two species of shrub in the Pityrodia genus, and the burning regime in both Kakadu and Keep River national parks is a major threat to the young grasshoppers, which are wingless as juveniles.
'Lyn has found that when the host plant is burnt, the young grasshopper may survive under rocks but will eventually die due to lack of food,' Dr Fletcher said.
'The host plant does not die but regenerates green and lush in a matter of weeks - but too late for the grasshopper.'
The grasshoppers are sedentary and may live out their one year life-cycle on a single shrub. Even as adults, the grasshoppers have limited dispersal ability because of the isolated patches of the food plant.
Bright colouration in insects usually warns predators that an insect is toxic or repellant in some way. Leichhardt's grasshopper has no known predators and has long been thought to contain a toxin although there has never been any evidence for this.
'Our research has found that although Leichhardt's grasshopper is possibly distasteful, it contains no obvious toxin,' Dr Fletcher said.
'We have found that it has virtually no jumping muscles, and shows little tendency to jump when threatened. This is consistent with an insect that has some form of chemical defence.
'It is the only species in the genus Petasida and so there are no closely-related species for comparison,' she said.
'This is the first chemical study of either the grasshopper or its host plants.
'We have isolated and identified a number of terpene and flavonoid compounds in the host plants. The grasshopper modifies some of these compounds during digestion, and these chemicals may play a role in the insect's defence and communication.'
Professor Kitching and Dr Fletcher's research concerns the chemical components of the host plants, the importance of the plants in the grasshopper's defence mechanisms, the role of the grasshopper's colour in its survival, and the use of pheromones for mating and aggregation.
For more information contact Professor Kitching on (07) 3365 3925 or Dr Fletcher on (07) 3365 3795.
