Subterranean termites such as Coptotermes formosanus Shiraki inhabit underground nests consisting of a complex network of galleries resulting in a highly modified environment relative to the surrounding soils. A healthy colony can maintain homeostatic conditions within the nest, limiting opportunities for pathogens, parasites, and predators to exploit the termite colony as a resource. However, a stressed or senescent colony can display a lack of nest maintenance, leading to the colonization of the nest as an opportunistic niche by other organisms. In this study, we described the nest colonization by microbes and arthropods during the collapse of three dying C. formosanus laboratory colonies. The carton nest and the tunnel lining that are mostly made out of termite fecal material were invaded by a variety of fungi, and Acari and Collembolan populations quickly increased during the senescence phase of the termite colony, presumably scavenging on the fungal material. Finally, the carton colonized by fungal mycelia hosted numerous larvae of a sciarid fly, Bradysia sp. (Diptera). This fungus gnat used the decomposing carton material as a breeding site, and numerous adults of this fly were found hovering above the dying termite colony. Bradysia larvae also showed infestation by parasitic nematodes, suggesting the presence of multiple trophic levels in the resource utilization of the nest of a declining termite colony. We concluded that a dying subterranean colony represents a resource opportunity for scavenging organisms and that the nest structure represents an opening niche that initiates an ecological succession.