Reporter expression is detected in stalk cells. By stage 9, staining can be detected in a large domain of posteriorly migrating main body follicle cells. By stage 10, expression is restricted to anterior follicle cells, especially those on the dorsal side of the egg. Expression is seen in anterior follicle cells secreting the collar and micropyle and in some of the cells that secrete the dorsal appendages.

In embryo, expression in anal pad not certain.

The enhancer trap staining pattern resembles that of 18w during germ band extension but becomes more complex due to the perdurance of the β-gal enzyme. In stage 14-16 embryos, expression is observed in ectodermal stripes that are 4-5 cells wide in each segment. Expression is also observed in most of the developing tracheal tree, salivary glands, anal pads, dorsal vessel, hindgut, pharynx, posterior spiracles, a small cluster of cells in each metamere of the CNS, and in some of the ventral muscles.