In aboriginal culture these grasshoppers are known as Alyurr, Children of the Lightning Man (Namarrgon). Namarrgon strikes the clouds with axes to bring the wondrous thunderstorms in the wet season and transformed the grasshoppers from a drab coloration to a brilliant one. Alyurr brought language, beliefs, and societal structure to the local people, and emerges during the ‘build-up’ to call to Namarrgon for the monsoon rains and storms. And sure enough, we encountered this grasshopper during a storm.
Leichhardt’s grasshopper (Petasida ephippigera) is endemic to the stone country of the Top End in the Northern Territory, and it belongs to the family Pyrgomorphidae, commonly known as the gaudy grasshoppers. The grasshopper is named after Ludwig Leichhard who documented mass aggregations of the species in 1845. Curiously, very few specimens were encountered by the turn of the century, and for the next 70 years they seemed to have completely vanished. It wasn’t until 1971 that small isolated populations were described along sandstone plateaus in Arnhem Land.
Leichhardt’s grasshopper feeds exclusively on three species of bushes in the genus Pityrodia (family Lamiaceae), pictured here on Pityrodia jamesii in Kakadu National Park. Upon hatching, nymphs will feed at the base of the plant and gradually move higher as they mature. This is partially the reason why Leichhardt’s grasshopper remains virtually undetected until it reaches adulthood. Pityrodia is known to have unpalatable glycoside compounds, and although the grasshoppers are able to tolerate the substances, the degree to which the supposedly aposematic grasshoppers are toxic remains to be investigated.
Oddly, unlike the grasshopper, their host plant is widespread. Ecological studies prove difficult for this species because of its low abundance and remote localities. However, controlled bush fires during the dry season could be harmful to the grasshopper’s survival. Pityrodia is fire tolerant and bounces back more quickly than other native plants, but during the month or so of scarce host plant availability, flightless grasshopper nymphs likely perish. If the fires are too intense there may be fewer unburnt patches providing refuges for the grasshoppers and the Pityrodia bushes may be exterminated for good. Aboriginal burning patterns — often less in intensity and frequency — may have been more forgiving to the life cycle of Leichhardt’s grasshopper while providing cyclical fires for the survival of Pityrodia.
Photographed in situ