EcollacZ reporter gene expression isobserved from embryonic stage 13. The pattern closely resembles labexpression in a thin stripe of cells in the midgut epithelium thatcoextends approximately with Ubx expression in parasegment 7 of theadhering visceral mesoderm. The stripe widens and displays a gradedpattern with the strongest expression posteriorly. As with labexpression, a 2-3 cell wide gap is present between the posterior boundaryof EcollacZ expression and the second midgut constriction.