Cell bcu (=cell cup, anal cell) is a small cell near the base of the wing. It is bordered by vein Cu anteriorly, by vein A1 posteriorly, and by vein Cu2 distally. In Anastrepha and Toxotrypana, vein Cu2 has a sharp bend, such that cell bcu has an elongate posterodistal lobe. The ratio of cell bcu is its total length, measured from its base at the juction of veins Cu and A1 to the apex of the posterodistal lobe, divided by the length of its anterior margin measured along vein Cu.