Biovector of arsenic Concerns have been raised over the potential role of agriculture in turning the bogong moth into a biovector of arsenic in the Australian Alps. Aggregations of bogong moths in aestivation sites has led to the bioaccumulation of the pollutant in both the surrounding local environment and within predators, particularly in the endangered mountain pygmy possum. However, no conclusive evidence has directly linked agriculture as the source of arsenic in bogong moths. In 2001, a few months after rainfall had washed out debris consisting of dead moths from within the cave, the complete death of local grasses was seen outside of an aestivation site of the bogong moth. Investigation into the causes of the grass mortality showed that the concentration of arsenic in the surrounding areas was much higher than normal, and the source was determined to be the bogong moths. Since the bogong moths do not feed at their aestivation sites, they had absorbed arsenic from lowland feeding sites as larvae and subsequently transported it over long distances into the mountains. Bioaccumulation, the absorption and accumulation of substances by organisms, occurs with arsenic in bogong moths. While levels within each individual moth are small, the sheer quantity of moths in the area led to a concentration of the pollutant to damaging levels in the environment. The presence of arsenic has also been shown in the feces of mammals such as the mountain pygmy-possum, demonstrating the bioaccumulation of this pollutant in animals. While no source has been determined, concerns have been raised over the possible role of agriculture in the bioaccumulation of arsenic due to its presence in historically and presently-used insecticides. This has led to the discontinued use of insecticides in controlling the bogong moth in urban areas, in favour of less intrusive methods. Decline in numbers In the spring and summer seasons of 2017-8 and 2018-9, dramatic drops in numbers of the moths in the Alpine caves have been observed. Millions of the moths have usually lined the walls of these caves over summer, but for the past two seasons there have been none in some caves, according to Professor Eric Warrant of Lund University in Sweden. He says that the drop in numbers was probably caused by a lack of rainfall due to winter drought in their breeding areas and climate change, the lack of rain producing insufficient vegetation to feed the caterpillars. Some caves