An ink cartridge includes at least one wall; an ink chamber capable of storing ink, the ink chamber being bounded, at least in part, by the at least one wall; an ink supply opening configured to permit communication between the ink chamber and an area outside of the ink chamber; and a detection portion. The detection portion extends away from the ink chamber relative to portions of the ink cartridge adjacent to the detection portion, at least when the ink cartridge is installed in an image forming apparatus; and at least one part of the detection portion is capable of obstructing at least a portion of a light beam directed through the detection portion.