A Tm1FBtr0091350:pb-XREcollacZ reporter construct with 1400 bp upstream sequence, the first exon, the first intron, and 72 bp of the second exon of Tm1 was expressed in all muscles of embryo, larvae, and adults. Expression is detected as early as stage 14 of embryogenesis, in the pharyngeal muscle of the head, and in body wall and visceral muscles. A similar construct with 1400 bp upstream sequence and 36 bp of the first exon, but missing the first intron, showed no expression.