An insect derived peat? The curious case of sediments at Bogong moth aestivation sites

The Bogong moth Agrotis infusa (Boisduval) is a migratory noctuid moth from south-eastern Australia which annually migrates thousands of kilometres for a period of aestivation in boulder-piles, caves and crevices on the highest mountain peaks of the Australian Alps. The same aestivation sites are used each year, and over time a highly organic deposit made predominately of preserved insect chiton and plant matter has accumulated at many of them. Examples of these sediments were characterised using a range of standard methods to ascertain the organic content, the carbon and nitrogen components, the lipids (oils and waxes) concentration and the acidity of each deposit. The deposits were found to be high in organic matter with a relatively high C:N ratio, low in lipids, and highly acidic. The acidity and amount of organic matter in these deposits are above threshold levels for classification as peat. The high concentration of insect remains, their taphonomic importance and the ecological context warrant the naming of sediments at Bogong moth aestivation sites as “insect derived peat” or “moth peat”.