Entomology definition of Costal cell: the area inclosed between the costal and
subcostal veins: in the plural, Comstock, are all the cells
anteriorly margined by the costa; in Hymenoptera (Norton),
includes the 1st, 2d and subcostal; of Packard, the 3d costal =
2d radial 1, and radial 2: in Diptera (Will.), it is the 2d
costal.