Oak apple due to the superficial resemblance and the preponderance of the oak marble gall in the wild. Other galls found on oak trees include the oak artichoke gall and the acorn cup gall, but each of these has its own distinctive form. Some common oak-apple-forming species are the "Biorhiza pallida" gall wasp in Europe, "Amphibolips confluenta" in eastern North America, and "Atrusca bella" in western North America. Oak apples may be brownish, yellowish, greenish, pinkish, or reddish. Oak galls have been used in the production of ink since at least the time of the Roman Empire. From the Middle Ages to
Royal Oak, Michigan income of $50,562 versus $36,392 for females. The per capita income for the city was $30,990. About 2.0% of families and 4.3% of the population were below the poverty line, including 3.4% of those under age 18 and 5.5% of those age 65 or over. Royal Oak has a Council-Manager form of government. It is governed by a city commission consisting of a mayor and six commission members. The city commission appoints a city manager, who manages the day-to-day operations of the city. Royal Oak has a below-average crime rate, similar to that of nearby upper middle-class communities, such as