Honeybee populations are in decline. The fall in the number of European honeybees, which are the main species used in beekeeping, is particularly pronounced. The main causes with direct impact, scientist's theories, are disease borne by varroa mites, and hornets, which are natural predators of honeybees. In contrast, the Japanese honeybee —— a subspecies native to Japan —— is resistant to varroa mites and employs a technique called the "hot defensive bee ball" to fight off hornets. Scientists say that genetic analysis of the Japanese honeybee could potentially be applied to its conservation and even to selective breeding of honeybees.