Mortality or more-tile-ity: Tiling response to temperature and humidity extremes in Agrotis infusa

Abstract

The bogong moth (Agrotis infusa) is one of Australia’s most famous insects, due in part to its spectacular tiling behaviour. The moths have great social and historical significance to Indigenous Australians from large portions of south-eastern Australia, and have been adopted as an icon by many modern groups and artists. These moths aestivate in rocky environments over summer, but often interact with human structures, bringing them spectacularly to the attention of the general public. Despite this, the exact mechanisms driving bogong moth tiling are unknown. The migratory lifestyle of the bogong moth enables moths to avoid the worst of temperature and humidity extremes during the Australian summer. However, conditions in the alpine and subalpine caves in which the moths prefer to aestivate are still intensely warm and dry, but with nights much cooler than the lower altitudes that the moths have left. While the purpose of the moths’ tiling behaviour is currently unknown, given these conditions it has been proposed that moths may tile to conserve moisture, heat or both. We exposed groups of moths to temperature extremes, while measuring tiling percentage and effectiveness, and also exposed moths either singly or in groups to extreme humidity, while measuring the same. Contrary to predictions, moths demonstrated both higher temperatures and higher moisture loss when tiling.