page_title: Bogong moth
section_title: Social aggregation
hierarchical_section_title: Bogong moth / Behaviour / Social aggregation
caption_attribution_description: English: The bogong moth (Agrotis infusa) migrates in large numbers each spring from the western slopes and plains of Victoria, NSW and Qld to the high country of eastern NSW and Vic. Westerly winds sometimes carry them out to the coast and sea, where large numbers perish. Otherwise, the moths progressively congregate at granite outcrops in deep crevices. They cluster in imbricate formation, sometimes emerging at dusk to make short trips, but rarely feeding. They return to the western slopes and plains the next Autumn.
context_page_description: The bogong moth is a temperate species of night-flying moth, notable for its biannual long-distance seasonal migrations towards and from the Australian Alps, similar to the diurnal monarch butterfly. During the autumn and winter it is found in southern Queensland, western New South Wales, western Victoria, and also in South and Western Australia. Adult bogong moths breed and larvae hatch during this period, consuming winter pasture plants during their growth. During the spring, the moths migrate south or east and reside in mountains such as Mount Bogong, where they gregariously aestivate over the summer until their return towards breeding grounds again in the autumn.
  The moth's name, bogong, is derived from the Australian Aboriginal Dhudhuroa word bugung, describing the brown colouration of the moth. It is an icon of Australian wildlife due to its historical role as an important food source and because aboriginal tribes would come to where the moths spend the summer to feast on them and hold intertribal gatherings.
context_section_description: During the spring migration, bogong moths gregariously aggregate with densities reaching 17,000 moths per square metre (10.8 square feet) within caves, crevices, and other areas hidden from the sunlight. The lack of light and relatively constant temperature and humidity makes these spots favourable during aestivation. The first moths that arrive occupy the deepest and darkest locations, using their fore tarsi to grip onto the rock faces, and aggregations form around these initial areas, with moths arriving later settling for less ideal areas with more sunlight, higher temperatures, and decreased humidity. To diminish the amount of light that reaches their light-sensitive eyes, later moths push themselves underneath the wings and abdomens of moths that arrived earlier and place their hind legs on top of the moths beneath them. This physical contact and aggregation allow the moths to retain body moisture. When the aestivating moths are disturbed, the moths within the area of disturbance briefly spread out and leave the aggregation, dropping excrement when unsettled before quickly returning to the aggregation and re-positioning themselves.
  While the moths mostly remain dormant during aestivation, there are some periods of activity within the aggregation which are correlated to changes in light intensity.  During dawn and dusk, portions of the population become active, first crawling around and spreading out, and then flying out of their shelter into the open. While some water drinking has been observed, no evidence of copulation or active foraging has been found during these periods of activity.
caption: Gregarious aggregation of bogong moths during aestivation
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