Four enhancer fragments drive GAL4 expression. The 3.0 kb fragment from P{Scr-GAL4.2}, the 8.9 kb fragment from P{Scr-GAL4.3} and the 0.8 kb and 8.5 kb fragments from P{Scr-GAL4.1} are arranged in the order 3.0 kb-8.9 kb-0.8 kb-8.5 kb-GAL4.
ScerGAL4Scr.4 drives strong expression in the embryonic labial and T1 segments, and in the anterior midgut.