populations of New South Wales do not migrate, and reach sexual maturity at a faster rate than migratory populations. Social aggregation 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. Diapause Facultative diapause, an optional period of delayed development in response to environmental conditions, accompanies the biannual migration of the bogong moths. While one generation of moths goes through the two migrations each year, multiple generations are possible in favourable conditions and higher temperatures, as growth across all life stages can occur faster. For example, without the diapause, the bogong moth would normally complete sexual maturation within 50 days. However, this maturation is delayed due to the lack of larval food sources during the summer season. During the summer, hot temperatures occur and grasses, which are an unfavourable diet for bogong moth larvae, overtake pastures and make up the majority of the plants occupying the pastures. Bogong moths avoid this harsh environment by delaying development during the summer so that their eggs do not