Biotic and abiotic factors experienced during development will affect developmental resource allocation leading to phenotypic variation, also referred to as developmental plasticity. As in all insects, environmental factors can influence several aspects of development in "Drosophila melanogaster". Fruit flies reared under a hypoxia treatment experience decreased thorax length, while hyperoxia produces smaller flight muscles, suggesting negative developmental effects of extreme oxygen levels. Circadian rhythms are also subject to developmental plasticity. Light conditions during development affect daily activity patterns in "Drosophila melanogaster", where flies raised under constant dark or light are less active as adults than those raised under a 12-hour light/dark cycle.